Overactive bladder syndrome and the potential role of prostaglandins and phosphodiesterases: an introduction

Vinpocetine Ameliorates Metabolic-Syndrome-Associated Bladder Overactivity in Fructose-Fed Rats by Restoring Succinate-Modulated cAMP Levels and Exerting Anti-Inflammatory Effects in the Bladder Detrusor Muscle

Succinate and its receptor, the G protein-coupled receptor 91 (GPR91), have pathological implications in metabolic syndrome (MetS) and its associated bladder dysfunction, particularly in decreasing bladder cAMP levels and promoting proinflammation. Using fructose-fed rats (FFRs), a rat model of MetS, we investigate the effects of vinpocetine (a phosphodiesterase-1 inhibitor) and celecoxib (a selective cyclooxygenase-2 inhibitor) on MetS-associated bladder overactivity. Phenotypes of the overactive bladder, including increased micturition frequency and a shortened intercontractile interval in cystometry, were observed in FFRs, together with elevated succinate levels in the liver and serum and the downregulation of GPR91 in the liver and urinary bladder. Treatments with vinpocetine and celecoxib improved tissue fibrosis and ameliorated the overexpression of the inflammatory cytokines, such as IL-1β, in the liver and bladder. In bladder organ bath studies, vinpocetine, but not celecoxib, treatment restored the contraction and relaxation responses of the detrusor muscle strip in response to KCl, carbachol, and forskolin stimulation. At a molecular level, vinpocetine and celecoxib treatments modulated the downstream messengers of GPR91 (i.e., ERK1/2 and JNK), suppressed NF-κB and IL-1β expressions in the bladder, and prevented the fibrogenesis observed in FFRs. The exogenous application of succinate to a bladder organ bath significantly reduced the forskolin-induced cAMP production by the detrusor muscle, which was notably restored in the presence of vinpocetine. Together, these results suggest that vinpocetine may alleviate the MetS-associated bladder overactivity by restoring the succinate-modulated detrusor cAMP production and exerting the anti-inflammatory effects in the bladder detrusor muscle.

Isoprostanes evoke contraction of the murine and human detrusor muscle via activation of the thromboxane prostanoid TP receptor and Rho kinase

Local or systemic inflammation can severely impair urinary bladder functions and contribute to the development of voiding disorders in millions of people worldwide. Isoprostanes are inflammatory lipid mediators that are upregulated in the blood and urine by oxidative stress and may potentially induce detrusor overactivity. The aim of the present study was to investigate the effects and signal transduction of isoprostanes in human and murine urinary bladders in order to provide potential pharmacological targets in detrusor overactivity. Contraction force was measured with a myograph in murine and human urinary bladder smooth muscle (UBSM) ex vivo. Isoprostane 8-iso-PGE₂ and 8-iso-PGF_2α evoked dose-dependent contraction in the murine UBSM, which was abolished in mice deficient in the thromboxane prostanoid (TP) receptor. The responses remained unaltered after removal of the mucosa or incubation with tetrodotoxin. Smooth muscle-specific deletion of Gα_12/13 protein or inhibition of Rho kinase by Y-27632 decreased the contractions. In Gα_q/11-knockout mice, responses were reduced and in the presence of Y-27632 abolished completely. In human UBSM, the TP agonist U-46619 evoked dose-dependent contractions. Neither atropine nor the purinergic receptor antagonist pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid decreased the effect, indicating that TP receptors directly mediate detrusor muscle contraction. 8-iso-PGE₂ and 8-iso-PGF_2α evoked dose-dependent contraction in the human UBSM, and these responses were abolished by the TP antagonist SQ-29548 and were decreased by Y-27632. Our results indicate that isoprostanes evoke contraction in murine and human urinary bladders, an effect mediated by the TP receptor. The G_12/13-Rho-Rho kinase pathway plays a significant role in mediating the contraction and therefore may be a potential therapeutic target in detrusor overactivity.NEW & NOTEWORTHY Voiding disorders affect millions of people worldwide. Inflammation can impair urinary bladder functions and contribute to the development of detrusor overactivity. The effects and signal transduction of inflammatory lipid mediator isoprostanes were studied in human and murine urinary bladders ex vivo. We found that isoprostanes evoke contraction, an effect mediated by thromboxane prostanoid receptors. The G_12/13-Rho-Rho kinase signaling pathway plays a significant role in mediating the contraction and therefore may be a potential therapeutic target.

Imbalance of nerve growth factor metabolism in aging women with overactive bladder syndrome

PURPOSE

Given the disputable link between nerve growth factor (NGF) and overactive bladder syndrome (OAB) and the lack of studies on its precursor (proNGF) in OAB, the aim of the study was to identify changes in the urinary levels of NGF and its proteolytic enzymes in aging women with OAB.

METHODS

We examined the urinary proNGF/NGF ratio and its processing enzymes in aging women (50-80 years), comparing 20 controls and 20 subjects with OAB.

RESULTS

In contrast to previous reports correlating NGF to OAB symptoms, we found that proNGF/NGF ratio in the OAB group was twice as high compared to controls (p = 0.009) with a lower NGF levels in women with OAB without statistical significance [1.36 (Q1, Q3: 0.668, 2.39) vs. 1.7 (Q1, Q3: 1.27, 3.045) pg/mg creatinine in control group, p = 0.05]. Enzymatic activity of MMP-7, the main enzyme for extracellular proNGF maturation, was significantly increased in the OAB group and correlated positively with scores of OAB symptoms questionnaires. However, this was counteracted by several-folds increase in the MMP-9 enzyme responsible for NGF proteolysis. While these findings highlight the importance of changes in the proteolytic enzymes to maintain proNGF/NGF balance in OAB, analysis of covariates showed that these changes were attributed to age, insulin resistance and renal function.

CONCLUSION

NGF proteolysis imbalance can be clinically meaningful in OAB related to aging, rendering it as a potential therapeutic target. However, other age-related factors such as insulin resistance and renal function may contribute to the relationship between NGF and aging-related OAB phenotype.

The profile of urinary biomarkers in overactive bladder

AIMS

In overactive bladder (OAB) research, different biomarkers have been proposed as diagnostic tools and may be used to create individual patient profiles. Assessing the diagnostic performance of biomarkers would better outline their utility. Therefore, our aim was to investigate the diagnostic value of four urinary biomarkers: human brain derived neurotrophic factor (hBDNF), malondialdehyde (MDA), h nerve growth factor (hNGF) and h 8-hydroxydeoxyguanosine in women with OAB. These are neurotrophins/oxidative stress markers that have been linked to lower urinary tract symptoms.

METHODS

A total of 105 women were included in the study and distributed in two groups: a group with OAB (n = 53) and a control group (n = 50). The levels of the biomarkers were determined using enzyme-linked immunosorbent assay technique and they were compared between the groups. If the Mann-Whitney test demonstrated a statistically significant difference, receiver operating curves (ROC) analysis was undertaken.

RESULTS

When normalized to urinary creatinine, hBDNF, MDA, and hNGF showed significantly increased values in women with OAB as compared to controls, whereas 8-OHdG showed no significant difference. The diagnostic performance of these biomarkers was analyzed based on the area under the ROC curve (AUC). MDA had the highest AUC (0.75), followed by hNGF (0.69) and hBDNF (0.67).

CONCLUSIONS

Our findings suggest that MDA, a relatively novel biomarker in OAB research, has a fair performance as a diagnostic tool for OAB. Moreover, urinary neurotrophins (NGF and BDNF) as biomarkers may have a role in the diagnostic pathways of women with OAB symptoms.

The five primary prostaglandins stimulate contractions and phasic activity of the urinary bladder urothelium, lamina propria and detrusor

Background

Inflammation is often associated with several bladder dysfunctions, including overactive bladder (OAB) and interstitial cystitis/bladder pain syndrome (IC/PBS). As such, inflammation of the bladder and the actions of inflammatory mediators may contribute to the development of urinary symptoms. This study assessed the actions of PGE₂, PGF₂, PGD₂, TXA₂, and PGI₂ on urinary bladder urothelium with lamina propria (U&LP), and detrusor smooth muscle.

Methods

Studies were carried out using isolated tissue baths, where strips of porcine bladder U&LP or detrusor were exposed to varying concentrations of prostaglandin agonists (1 μM and 10 μM).

Results

All assessed prostaglandin agonists contracted both the U&LP and detrusor smooth muscle, with the rank order of contractile response effectiveness as: PGE₂ > PGF_2α > TXA₂ > PGD₂ > PGI₂. In U&LP, treatment with PGE₂ (10 μM) increased tonic contractions by 1.36 ± 0.09 g (n = 42, p < 0.001) and phasic contractions by 40.4 ± 9.6% (n = 42, p < 0.001). In response to PGF_2α (10 μM), U&LP tonic contractions increased by 0.79 ± 0.06 g (n = 14, p < 0.001) and phasic activity by 13.3% ± 5.3% (n = 15, p < 0.05). In detrusor preparations, PGE₂ (10 μM) increased tonic contractions by 1.32 ± 0.13 g (n = 38, p < 0.001) and PGF_2α (10 μM) by 0.97 ± 0.14 g (n = 12, p < 0.001). Only 34% (n = 48) of all detrusor preparations exhibited spontaneous activity prior to the addition of any agonist at a frequency of 2.03 ± 0.12 cpm. In preparations that did not exhibit initial phasic activity, all of the prostaglandin agonists were capable of commencing phasic activity.

Conclusions

The urinary bladder U&LP and detrusor respond to a variety of prostaglandin agonists, with their activation resulting in direct contractions, as well as increases to spontaneous contractile activity. This study presents the prostaglandin receptor system as a potential therapeutic target for lower urinary tract dysfunction.

Neuromodulation for functional bladder disorders in patients with multiple sclerosis

The function of the lower urinary tract is mainly storage and voiding of urine, which is coordinated by the nervous system. Various diseases of the nervous system may cause neuro-urological symptoms. Neuro-urological symptoms depend on the localization of the disease and the extension of the neurological lesion. About 80% of multiple sclerosis (MS) patients have neuro-urological symptoms within 10 years after diagnosis. In addition, 10% of MS patients may even present with voiding dysfunction at disease onset. In this review, different types of neuromodulation are discussed. The available studies suggest that sacral neuromodulation (SNM) and percutaneous tibial nerve stimulation (PTNS) may be helpful in the neuromodulation of MS-related overactive bladder symptoms. These techniques may not only decrease the severity of symptoms but also significantly improve the quality of life of affected patients. Exploring the role of implantable tibial nerve stimulation devices in patients with MS could open new doors in the management of urgency and urgency incontinence in this patient group.

Avanafil Inhibits the Contractility of the Isolated Caprine Detrusor Muscle

Context:

Avanafil is a smooth muscle relaxant that is clinically used to treat erectile dysfunction. It is an inhibitor of phosphodiesterase-5 (PDE5), the enzyme that catalyzes the metabolism of cyclic guanosine monophosphate (cGMP). The inhibitory effect of avanafil on isolated detrusor muscle contractility has not been studied.

Aims:

This study investigated the inhibitory effect of avanafil on isolated caprine (goat) detrusor muscle contractility and the possible mechanisms involved.

Settings and Design:

80 mM potassium chloride (KCl)-induced contractility of the isolated goat detrusor was studied using a physiograph.

Materials and Methods:

Ten caprine detrusor strips were made to contract using 80 mM KCl before and after addition of three concentrations (10, 30, and 60 μM) of avanafil. Three reversal agents, ODQ, a guanylyl cyclase inhibitor; glibenclamide, an adenosine triphosphate (ATP)-sensitive potassium channel blocker; and iberiotoxin, a calcium-sensitive potassium (BKCa) channel blocker, were investigated for their ability to reverse the inhibitory effect of 30 μM avanafil on KCl-induced detrusor contractility.

Statistical Analysis Used:

The nonparametric statistical test, Kruskal–Wallis test, was used for the analysis of the data.

Results:

Avanafil caused a statistically significant inhibition of detrusor contractility at 30 and 60 μM concentrations. The inhibitory effect of 30 μM avanafil on detrusor contractility was significantly reversed by the addition of ODQ, glibenclamide, and iberiotoxin.

Conclusions:

Avanafil inhibits the contractility of the isolated detrusor by inhibiting PDE5, leading to raised cellular levels of cGMP. The raised levels of cGMP could have inhibited detrusor contractility by activating cGMP-dependent protein kinase, by opening ATP-sensitive potassium channels, and by opening BKCa. Avanafil could be evaluated for treating clinical conditions requiring relaxation of the detrusor like overactive bladder.

Castration increases PGE2 release from the bladder epithelium in male rats

AIMS

Androgen deprivation therapy has been widely used for the treatment of prostate cancer. While sexual side effects including decreased sexual desire and function are well studied, there are only limited reports about its influences on lower urinary tract symptoms. The aim of this study is to clarify the influences of castration in male rats.

METHODS

Ten-week-old male rats were divided into treatment group (bilateral orchiectomy) and control group (sham surgery). Two-months after the surgery, adenosine triphosphate (ATP), prostaglandin E2 (PGE2), and nerve growth factor (NGF) released from stretched bladder epithelium were measured by luciferin-luciferase assay or ELISA. The mRNA levels of bladder cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) were determined by real-time PCR. The protein level of bladder COX-2 was analyzed by western blot analysis. Bio-Plex Pro cytokine assay was performed to quantify the level of proinflammatory cytokine interleukin (IL)-1β in the bladder.

RESULTS

The PGE₂ release from stretched bladder epithelium was significantly increased after castration, which increased more than 50% compared with control. On the other hand, those of ATP and NGF were not different from those of the controls. Testosterone replacement restored the PGE₂ increase. Castration significantly increased bladder IL-1β protein level and COX-2 at both mRNA and protein levels, whereas caused no marked changes in the COX-1 mRNA level.

CONCLUSIONS

These findings suggest that castration induces inflammation in the rat bladder, which causes elevated PGE₂ release from bladder epithelium and may finally contribute to the disruption of bladder storage function.

Low amplitude rhythmic contraction frequency in human detrusor strips correlates with phasic intravesical pressure waves

PURPOSE

Low amplitude rhythmic contractions (LARC) occur in detrusor smooth muscle and may play a role in storage disorders such as overactive bladder and detrusor overactivity. The purpose of this study was to determine whether LARC frequencies identified in vitro from strips of human urinary bladder tissue correlate with in vivo LARC frequencies, visualized as phasic intravesical pressure (p _ves) waves during urodynamics (UD).

METHODS

After IRB approval, fresh strips of human urinary bladder were obtained from patients. LARC was recorded with tissue strips at low tension (<2 g) and analyzed by fast Fourier transform (FFT) to identify LARC signal frequencies. Blinded UD tracings were retrospectively reviewed for signs of LARC on the p _ves tracing during filling and were analyzed via FFT.

RESULTS

Distinct LARC frequencies were identified in 100% of tissue strips (n = 9) obtained with a mean frequency of 1.97 ± 0.47 cycles/min (33 ± 8 mHz). Out of 100 consecutive UD studies reviewed, 35 visually displayed phasic p _ves waves. In 12/35 (34%), real p _ves signals were present that were independent of abdominal activity. Average UD LARC frequency was 2.34 ± 0.36 cycles/min (39 ± 6 mHz) which was similar to tissue LARC frequencies (p = 0.50). A majority (83%) of the UD cohort with LARC signals also demonstrated detrusor overactivity.

CONCLUSIONS

During UD, a subset of patients displayed phasic p _ves waves with a distinct rhythmic frequency similar to the in vitro LARC frequency quantified in human urinary bladder tissue strips. Further refinements of this technique may help identify subsets of individuals with LARC-mediated storage disorders.

5-HT2A receptor enhancement of contractile activity of the porcine urothelium and lamina propria

OBJECTIVES

To examine the effect of 5-hydroxytryptamine (5-HT; serotonin) on the contractile properties of the urothelium and lamina propria, as a better understanding of bladder physiology might aid the development of new treatments.

METHODS

Strips of porcine urothelium and lamina propria were suspended in gassed Krebs-bicarbonate solution, and cumulative concentration-response curves for 5-HT were generated in the absence and presence of 5-HT antagonists, Nω-nitro-l-arginine and indomethacin. Responses to α-methyl-5-HT were also examined.

RESULTS

Strips of urothelium/lamina propria developed spontaneous contractions, whereas the addition of 5-HT induced concentration-dependent increases in contractile tone with maximal contractions of 50.43 ± 2.78 mN/g tissue weight (n = 100). Tonic contractions to 5-HT were unchanged in the presence of Nω-nitro-l-arginine (100 μmol/L) or indomethacin (5 μmol/L). Selective concentrations of the antagonists methiothepin (5-HT_1&2 , 100 nmol/L), RS102221 (5-HT_2C , 30 nmol/L), ondansetron (5-HT₃ , 30 nmol/L), GR113808, (5-HT₄ , 100 nmol/L), SB699551 (5-HT₅ , 10 nmol/L), SB399885 (5-HT₆ , 100 nmol/L) and SB269970 (5-HT₇ , 10 nmol/L) did not influence responses to 5-HT. However, the 5-HT_2A antagonist, ketanserin (30-300 μmol/L), caused a shift of the 5-HT curve yielding an affinity estimate of 7.9.

CONCLUSIONS

The results show that contractile responses of the urothelium/lamina propria to 5-HT are predominantly mediated through the 5-HT_2A receptor.

Pirt reduces bladder overactivity by inhibiting purinergic receptor P2X3

Pirt is a transmembrane protein predominantly expressed in peripheral neurons. However, the physiological and pathological roles of Pirt in hollow viscus are largely unknown. Here we show that Pirt deficiency in mice causes bladder overactivity. The density of α,β-meATP-induced currents is significantly reinforced in Pirt-deficient dorsal root ganglion (DRG) neurons. Pirt and P2X3 receptor co-localize in bladder nerve fibres and heterologous Pirt expression significantly reduces P2X3-mediated currents. Pirt interacts with P2X3 through the N-terminal 14 amino-acid residues. TAT-conjugated Pirt(N14) peptide (Pirt(N14)) is sufficient to inhibit P2X3 activation in bladder DRG neurons and to alleviate bladder overactivity in Pirt(-/-) mice. Pirt expression is decreased in the bladder of cyclophosphamide (CYP)-treated mice, a commonly used model of bladder overactivity. Importantly, Pirt(N14) administration reduces the frequency of bladder voiding and restores the voided volume of CYP-treated mice. Therefore, our results demonstrate that Pirt is an endogenous regulator of P2X3 in bladder function.

Physiological and pathophysiological implications of micromotion activity in urinary bladder function

'Micromotions' is a term signifying the presence of localized microcontractions and microelongations, alongside non-motile areas. The motile areas tend to shift over the bladder surface with time, and the intravesical pressure reflects moment-by-moment summation of the interplay between net contractile force generated by micromotions and general bladder tone. Functionally, the bladder structure may comprise modules with variable linkage, which supports presence of localized micromotions (no functional linkage between modules), propagating contractions (where emergence of linkage allows sequential activation) and the shifting of micromotions over time. Detrusor muscle, interstitial cells and intramural innervation have properties potentially relevant for initiating, coordinating and modulating micromotions. Conceptually, such activity could facilitate the generation of afferent activity (filling state reporting) in the absence of intravesical pressure change and the ability to transition to voiding at any bladder volume. This autonomous activity is an intrinsic property, seen in various experimental contexts including the clinical setting of human (female) overactive bladder. 'Disinhibited autonomy' may explain the obvious micromotions in isolated bladders and perhaps contribute clinically in neurological disease causing detrusor overactivity. Furthermore, any process that could increase the initiation or propagation of microcontractions might be anticipated to have a functional effect, increasing the likelihood of urinary urgency and detrusor overactivity respectively. Thus, models of bladder outlet obstruction, neurological trauma and ageing provide a useful framework for detecting cellular changes in smooth muscle, interstitial cells and innervation, and the consequent effects on micromotions.

Effect of phosphodiesterase inhibitors in the bladder

Many aging men will experience lower urinary tract symptoms (LUTS). Phosphodiesterase type 5 (PDE5) inhibitors have shown promise in treating LUTS in these patients. PDE5 inhibitors mediate their effects through several pathways including cAMP, NO/cGMP, K-channel modulated pathways, and the l-cysteine/H₂S pathway. PDE5 inhibitors exert their effect in muscle cells, nerve fibers, and interstitial cells (ICs). The use of PDE5 inhibitors led to improvement in LUTS. This included urodynamic parameters. PDE5 inhibitors may play a significant role in LUTS due to their effect on the bladder rather than the prostate.

PATTERN OF OVERACTIVE BLADDER IN SOUTHEAST NIGERIA

BACKGROUND

Overactive bladder is a distressing condition characterized by the syndrome of uncontrollable urgency, day time frequency, nocturia with or without urgency urinary incontinence.

AIM

To determine the pattern of overactive bladder in two tertiary health institutions in South-East Nigeria.

STUDY DESIGN

The study is prospective.

SETTING

Federal Teaching Hospital, Abakaliki and Niger Foundation Hospital and Diagnostic centre Enugu in southeastern Nigeria.

METHOD

The study involved 383 patients who were diagnosed with overactive bladder in the two hospitals during the study period. Their demographics, clinical feature, management options and outcome were analyzed.Tolterodine was the anticholinegic used to treat the syndrome while the underlying pathology was treated accordingly.

RESULT

There were 383 patients out of which 363 (94.8%) patients were males while 20 (5.2%) patients were females with the age range of 37yrs to103yrs with a mean of 63.4yrs. A total of 313 (81.7%) patients had prostatic disease (benign prostatic hyperplasia and cancer of the prostate), while 99 (25.8%) patients had diabetes mellitus. Among the 313(82 %) with prostate disease, two hundred and eighty nine (75.5%) had benign prostatic hyperplasia while twenty four (6.3%) had cancer of the prostate. Urgency, urinary incontinence and fecal incontinence were observed simultaneously in 133 (34.7%) patients during the episode of involuntary painful bladder contraction. In 271 (71%) patients, the overactive bladder was treated with Tolterodine alone and management of the underlying pathology with resolution of symptoms. Few patients benefitted from behavioral therapy.

CONCLUSION

Overactive bladder in this environment is associated commonly with prostate diseases with urgency of urine, urine and fecal incontinence but responds well to anticholinergic.