Detrusor myocyte activity and afferent signaling

Statin administration ameliorates ischemia-induced overactive bladder with improvement of blood flow and anti-inflammatory effects in rats

AIMS

Statins are widely used to treat dyslipidemia and have been shown to reduce the risk of ischemic heart disease and cerebrovascular disease. The effects of statins on ischemia-induced overactive bladder (OAB) and the associated mechanisms were investigated in a rat model of chronic pelvic ischemia.

METHODS

A pelvic ischemia model was created by iliac arterial injury (AI) and a high-fat diet using male Sprague-Dawley rats. Rats were assigned to 3 groups: control group, AI group, and AI + statin group. The control group underwent sham operation and was fed a normal diet. The AI group underwent AI surgery and was fed a high-cholesterol diet. The AI + statin group was administered a statin for 4 weeks. Cystometry was performed for 8 weeks after surgery. Blood flow was evaluated by laser meter. Thickness of the iliac arteries was measured, and microvascular density in the lamina propria was evaluated by immunostaining for CD31. Expressions of inflammatory cytokines in the bladder were measured by real-time PCR.

RESULTS

Cystometry showed a significantly shorter voiding interval and lower bladder capacity in the AI group than in the control group. The AI + statin group showed improvement of these findings. The AI group showed decreased bladder blood flow, increased iliac arterial wall thickening, and decreased microvascular density compared to the control group. Statin administration improved blood flow. Iliac arterial wall thickening was suppressed, and microvascular density was increased by statin administration, though not significantly. Real-time PCR showed significantly higher expressions of inflammatory cytokines (IL-6, IL-8, and TNF-α) in the AI group than in the control group, and IL-6 and IL-8 expressions were lower in the AI + statin group than in the AI group.

CONCLUSIONS

The present results suggest that statins are effective in OAB caused by arteriosclerosis and ischemia. The mechanism of their effects involves improved bladder blood flow and decreased bladder inflammation.

Medicinal plants and natural products for treating overactive bladder

BACKGROUND

Overactive bladder (OAB) presents a high prevalence of 16-18% worldwide. The pathophysiology of OAB is still poorly understood while effective therapy or countermeasure are very limited. On the other hand, medicinal plants and herbal remedies have been utilized for treating lower urinary tract symptoms (LUTS) in both Eastern and Western cultures since ancient times. In recent years, accumulating progress has also been made in OAB treatment research by using medicinal plants.

METHODS

Relevant literature on the studies of medicinal plants and herbs used to treat OAB was reviewed. The medicinal plants were summarized and categorized into two groups, single-herb medications and herbal formulations.

RESULTS

The present review has summarized current understanding of OAB's pathophysiology, its available treatments and new drug targets. Medicinal plants and natural products which have been used or have shown potential for OAB treatment were updated and comprehensively categorized. Studies on a wide variety of medicinal plants showed promising results, although only a few phytochemicals have been isolated and identified. Until now, none of these herbal compounds have been further developed into clinical therapeutics for OAB.

CONCLUSIONS

This review provides the basis for discovering and designing new phytopharmaceutical candidates with effective and well-tolerated properties to treat OAB. Increasing evidences indicate new strategies with alternative herbal treatment for OAB have high efficacy and safety, showing great promise for their clinical use. Future studies in a rigorously designed controlled manner will be beneficial to further support the eligibility of herbal treatment as OAB therapeutics.

Comparison of tramadol and lornoxicam for the prevention of postoperative catheter-related bladder discomfort: a randomized controlled trial

BACKGROUND

Catheter-related bladder discomfort (CRBD is a painful complication of intraoperative urinary catheterization after anaesthesia. We conducted this study to compare the effect of tramadol and lornoxicam for the prevention of postoperative CRBD.

METHODS

One-hundred twenty patients (aged 18-60 years, ASA physical status 1-2, undergoing elective uterine surgery requiring intraoperative urinary catheterization were randomly divided into three groups with 40 patients in each group. Group T received 1.5 mg/kg tramadol, group L received 8-mg lornoxicam, and group C received normal saline. The study drugs were administered intravenously at the end of the surgery. The incidence and severity of CRBD were reported at 0, 1, 2, and 6 h after arrival at the postanaesthesia care unit (PACU).

RESULTS

The incidence of CRBD was significantly lower in groups T and L than in group C at 1, 2, and 6 h after surgery. The incidence of moderate to severe CRBD was also significantly lower in groups T and L than in group C at 0, 1, and 2 h after surgery. The severity of CRBD reported as mild, moderate, and severe was reduced in groups T and L compared with group C at most times after surgery. Group T had a higher incidence of nausea than group C, and there were no differences in dizziness, drowsiness, or vomit among the three groups.

CONCLUSIONS

Tramadol and lornoxicam administered intravenously at the end of the surgery were both effective in preventing the incidence and severity of CRBD after uterine surgery. However, tramadol increased the incidence of nausea compared with saline, but there was no difference between tramadol and lornoxicam.

TRIAL REGISTRATION

ChiCTR2100052003. Registered on 12/10/2021.

Inhibition of prejunctional parasympathetic pathways by β3-adrenoceptor agonists in the isolated pig detrusor: comparison with human detrusor studies

Adrenergic receptors of the β₃-subtype (β₃-ADRs) seem to represent a new target for a more effective pharmacological treatment of overactive bladder (OAB), a wide spread urinary disorder. A promising opportunity for OAB therapy might rely on the development of selective β₃-ADR agonists, but an appropriate preclinical screening, as well as investigation of their pharmacological mechanism(s), is limited by poor availability of human bladder samples and of translational animal models. In this study, we used the porcine urinary bladder as experimental tool to ascertain the functions of β₃-ADRs in the control the parasympathetic motor drive. Tritiated acetylcholine ([³H]-ACh), mainly originated from neural stores, was released by electrical field stimulation (EFS) in epithelium-deprived detrusor strips from pigs bred without estrogens. EFS produced simultaneously [³H]-ACh release and smooth muscle contraction allowing to asses neural (pre-junctional) and myogenic (postjunctional) effects in the same experiment. Isoprenaline and mirabegron produced on the EFS-evoked effects a concentration-dependent inhibition antagonized by L-748,337, a high selective β₃-ADR antagonist. The analysis of the resultant pharmacodynamic parameters supports the notion that in pig detrusors, as well as in previously described human detrusors, the activation of inhibitory β₃-ADRs can modulate neural parasympathetic pathways. In such inhibitory control, the involvement of membrane K⁺ channels, mainly of the SK type, seems to play a pivotal role similarly to what previously described in humans. Therefore, the isolated porcine detrusor can provide a suitable experimental tool to study the mechanisms underlying the clinical efficacy of selective β₃-ADR compounds for human use.

Microhematuria in Women Presenting for Overactive Bladder

PURPOSE OF REVIEW

Microscopic hematuria and overactive bladder are two common urologic conditions. The objective of this review is to provide an overview of current literature as well as highlight important guidelines that will aid physicians in the diagnostic workup of microscopic hematuria in patients experiencing symptoms of overactive bladder.

RECENT FINDINGS

Updated microscopic hematuria guidelines provide a structured and appropriate workup for women based on risk factors, which stratifies patients to prevent unnecessary procedures and imaging. Women presenting with microscopic hematuria in the setting of overactive bladder should undergo microscopic hematuria workup according to their risk stratification while receiving appropriate treatment for their overactive bladder. The physician should consider the presence of irritative voiding symptoms during the investigation and management of microscopic hematuria in patients with overactive bladder and should not delay overactive bladder treatment due to the presence of microscopic hematuria.

Oxidative Stress and Its Relation to Lower Urinary Tract Symptoms

The aim of this review is to discuss how to link lower urinary tract symptoms (LUTS) and oxidative stress (OS) and to define relevant targets for therapeutic intervention. Narrative review based on published literature. Many of the multifactorial pathophysiological mechanisms behind LUTS can initiate reactive oxygen species (ROS) generation. Assuming that OS is a consequence rather than a primary cause of LUTS it seems reasonable to identify both the disease mechanism initiating LUTS, and the source of ROS involved. There are many possible sources of ROS overproduction, but the NADPH oxidase (NOX) family of enzymes is the primary source; NOX activation in turn, may result in the activation of secondary ROS sources, i.e., ROS-dependent ROS production. Selective NOX inhibition therefore seems an attractive therapeutic strategy in LUTS treatment. The finding of NOX2 localization to centers in the brain associated with micturition control, opens up for further studies of NOX involvement in the central control of micturition, normally and in disease. Further information on the localization of the different isoforms of NOX in the LUT e.g., the bladder wall and its components and the prostate, is desirable. To optimize treatment, the pathophysiological mechanism initiating LUTS, and the activated isoform of NOX, should be identified. Unfortunately, in most cases of LUTS this is currently not possible. Even if selective NOX inhibitors have entered the clinical trial stage for treatment of disorders other than LUT dysfunction, their efficacy for LUTS treatment has to be demonstrated. If this can be achieved, an attractive approach would be combination of selective NOX inhibition with established drug therapies.

Effect of Bladder Injection of OnabotulinumtoxinA on the Central Expression of Genes Associated with the Control of the Lower Urinary Tract: A Study in Normal Rats

To investigate a possible central mechanism of action of Botulinum toxin A (BoNT/A) following injection in the bladder, complementary to the acknowledged peripheral bladder effect, we studied changes in the expression of neuropeptides and receptors involved in lower urinary tract function in the spinal cord (SC) and dorsal root ganglia (DRG) of normal rats following BoNT/A bladder injection. Thirty-six Sprague-Dawley rats, divided into three groups of n = 12, received bladder injections of 2U or 5U OnabotulinumtoxinA (BOTOX^®), or saline. Six animals from each group were sacrificed on days 7 and 14. Expression of Tachykinin 1 (Tac1), capsaicin receptor (TRPV1), neuropeptide Y (NPY), proenkephalin (PENK) and muscarinic receptors M1, M2, M3, was evaluated in the bladder, L6-S1 DRG, and SC segments using real-time PCR and Western blotting. Real-time PCR revealed increased expression of NPY in all tissues except for SC, and increased TRPV1 and PENK expression in DRG and SC, whereas expression of Tac1, M1 and M2 was decreased. Less significant changes were noted in protein levels. These findings suggest that bladder injections of OnabotulinumtoxinA may be followed by changes in the expression of sensory, sympathetic and cholinergic bladder function regulators at the DRG/SC level.

The efficacy and safety of antimuscarinics for the prevention or treatment of catheter-related bladder discomfort: a systematic review and meta-analysis of randomized controlled trials

OBJECTIVES

This meta-analysis aimed to evaluate the efficacy and safety of antimuscarinics for the prevention or treatment of catheter related bladder discomfort (CRBD).

METHODS

The MEDLINE, EMBASE, and Cochrane Controlled Trials Register (from 1987 to July 2021) were used to search randomized controlled trials. The PRISMA checklists were followed. RevMan5.4.0 was used for statistical analysis.

RESULTS

Eleven studies involving 1165 patients were involved in the analysis. The study reported that the incidence of CRBD observed in the antimuscarinics group was significantly lower than that of the control group at 0-, 1-, 2-, and 6-h after drug therapy (P = 0.001, P < 0.0001, P = 0.0005, and P = 0.001, respectively). For side effects, there were not statistical differences between the antimuscarinics group and the control group, mainly including dry mouth (risk ratio (RR) = 1.31, 95% confidence interval (CI) = 0.95 to 1.80, P = 0.09), postoperative nausea and vomiting (RR = 1.02, 95% CI = 0.55 to 1.90, P = 0.87), facial flushing (RR = 1.06, 95% CI = 0.43 to 2.61, P = 0.90), and blurred vision (RR = 0.95, 95% CI = 0.35 to 2.58, P = 0.91). Besides, rescue analgesics were required less in the antimuscarinics group than in the control group (RR = 0.51, 95% CI = 0.32 to 0.80, P = 0.003).

CONCLUSIONS

Compared with the control group, the antimuscarinics group had a significant improvement on CRBD, the patients were well tolerated and the use rate of rescue analgesics was low.

Gene Therapy for Overactive Bladder: A Review of BK-Channel α-Subunit Gene Transfer

A need exists for local (ie, bladder-specific) interventions to treat overactive bladder (OAB) with low risk of unwanted postprocedural outcomes. Gene therapy targeted to leverage endogenous physiology in bladder cells may assist in restoring normal cell and organ function. Herein, we review the potential promise of gene therapy for treating OAB, focusing on gene transfer of URO-902, a non-viral naked plasmid DNA expressing the big potassium (BK) channel. We searched PubMed for articles concerning functional aspects of the BK channel and its potential use for gene transfer as local OAB treatment. Results from preclinical, phase 1, and phase 2 studies of URO-902 for erectile dysfunction and phase 1 studies of URO-902 for OAB are included. The BK channel has been extensively studied; however, URO-902 is the first gene therapy used in clinical trials directed toward treating OAB via the BK channel. In both URO-902 studies, there were no serious adverse events considered treatment related and no adverse events leading to early withdrawal. Both studies included secondary efficacy endpoints with promising results suggesting improvement in OAB symptoms, and quality of life, with use of URO-902 versus placebo. Gene therapy involving the BK channel, such as gene transfer with URO-902, has demonstrated promising safety and efficacy results in women with OAB. Findings warrant further investigation of the use of URO-902 for OAB treatment.

Asiatic Acid, a Natural Compound that Exerts Beneficial Effects on the Cystometric and Biochemical Parameters in the Retinyl Acetate-Induced Model of Detrusor Overactivity

Scientists have been constantly looking for new synthetic and natural compounds that could have beneficial effects in bladder overactivity. Our attention was drawn by asiatic acid that influences a number of molecules and signaling pathways relevant for the proper functioning of the urinary tracts in humans. In the present project we wanted to check whether asiatic acid would have positive effects in the confirmed animal model of detrusor overactivity (DO) and whether it would affect the bladder blood flow, urothelium thickness, inflammatory and oxidative stress markers, neurotrophic and growth factors, and other parameters important for the activity of the urinary bladder. The outcomes of our study showed that a 14-day administration of asiatic acid (30 mg/kg/day) by oral gavage normalizes the cystometric parameters corresponding to DO and reduces the accompanying oxidative stress (measured by the levels of malondialdehyde–61,344 ± 24,908 pg/ml vs. 33,668 ± 5,071 pg/ml, 3-nitrotyrosine–64,615 ± 25,433 pg/ml vs. 6,563 ± 1,736 pg/ml, and NOS2–2,506 ± 411.7 vs. 3,824 ± 470.1 pg/ml). Moreover, it decreases the urinary secretion of neurotrophins (BDNF–304.4 ± 33.21 pg/ml vs. 119.3 ± 11.49 pg/ml and NGF–205.5 ± 18.50 vs. 109.7 ± 15.94 pg/ml) and prevents the changes in a range of biomarkers indicating the dysfunction of the urinary bladder, CGRP (421.1 ± 56.64 vs. 108.1 ± 11.73 pg/ml), E-Cadherin (773.5 ± 177.5 pg/ml vs. 1,560 ± 154.5 pg/ml), OCT3 (3,943 ± 814.6 vs. 1,018 ± 97.07 pg/ml), SNAP-23 (6,763 ± 808.9 pg/ml vs. 3,455 ± 554.5 pg/ml), SNAP-25 (2,038 ± 162.7 pg/ml vs. 833.3 ± 65.48), substance P (171.7 ± 16.86 pg/ml vs. 65.07 ± 8.250 pg/ml), SV2A (1,927 ± 175.3 pg/ml vs. 1,154 ± 254.9 pg/ml), tight junction protein 1 (360.1 ± 95.05 pg/ml vs. 563.4 ± 65.43 pg/ml), VAChT (16,470 ± 2,419 pg/ml vs. 7,072 ± 1,339 pg/ml), VEGFA (318.3 ± 37.89 pg/ml vs. 201.5 ± 22.91 pg/ml). The mentioned parameters are associated with smooth muscle contractions, urothelial barrier, transportation and release of transmitters, or bladder compensation. Thus, the presented findings allow to suggest a possible future role of asiatic acid in the prevention of conditions accompanied by DO, such as overactive bladder.

Intravesical dexmedetomidine instillation reduces postoperative catheter-related bladder discomfort in male patients under general anesthesia: a randomized controlled study

Background

The catheter-related bladder discomfort (CRBD) of male patients is a common clinical problem, albeit lacking effective solutions. The present study aimed to investigate whether intravesical dexmedetomidine instillation alleviates the postoperative urinary discomfort in male patients with catheter under general anesthesia.

Methods

This single-blinded, prospective, randomized study included a total of 167 male patients American Society of Anesthesiologists (ASA) physical status I-II scheduled for surgery under general anesthesia were allocated to two groups: 84 in the dexmedetomidine group and 83 in the control group. Dexmedetomidine group patients received intravesical instillation of the drug 0.5 μg/kg and normal saline 20 mL, while the control group received intravesical instillation of 20 mL normal saline. The catheter was clamped for 30 min after intravesical instillation for all patients. CRBD scores and urethra pain numerical rating scale (NRS) scores were measured at admittance to post-anesthesia care unit (PACU) (T0), intravesical instillation (T1), 30 min (T2), 60 min (T3), 2 h (T4) after intravesical instillation, discharged from PACU (T5), and 6 h (T6) and 24 h (T7) after the operation. Patient satisfaction at discharge from PACU and 24 h post-operation were compared between the two groups.

Results

CRBD scores and urethra pain NRS scores after 30 min of intravesical dexmedetomidine instillation to 24 h post-operation were significantly lower than the control group (p < 0.001), and patient satisfaction was higher at discharge from PACU and 24 h post-operation (p < 0.001). No differences were detected in Steward score out of PACU (p = 0.213) and from the time of the end of operation to fully awake (p = 0.417).

Conclusion

Intravesical dexmedetomidine instillation reduces postoperative urinary discomfort and urethra pain and improves satisfaction in male patients under general anesthesia.

Trial registration

Chinese Clinical Trial Registry (No. ChiCTR1800016429), date of registration 1st June 2018.

Prostaglandin E2 and F2alpha Modulate Urinary Bladder Urothelium, Lamina Propria and Detrusor Contractility via the FP Receptor

Current pharmacological treatment options for many bladder contractile dysfunctions are not suitable for all patients, thereby bringing interest to the investigation of therapies that target a combination of receptors. This study aimed to compare responses of PGE₂ on the urinary bladder urothelium with lamina propria (U&LP, also called the bladder mucosa) or detrusor smooth muscle and attempt to identify the receptor subtypes mediating PGE₂ contractile responses in these tissues. In the presence of selective EP1 – 4 receptor antagonists, varying concentrations of PGE₂ were applied to isolated strips of porcine U&LP and detrusor that were mounted in organ baths filled with Krebs-bicarbonate solution and gassed with carbogen. The addition of PGE₂ (1 and 10 μM) and PGF_2α (10 μM) to U&LP preparations caused significant increases in the baseline tension and in the spontaneous phasic contractile frequency. In detrusor preparations, significant increases in the baseline tension were observed in response to PGE₂ (1 and 10 μM) and PGF_α (10 μM), and spontaneous phasic contractions were initiated in 83% of preparations. None of the selective PGE₂ receptor antagonists inhibited the increases in baseline tension in both U&LP and detrusor. However, the antagonism of PGF_2α receptor showed significantly inhibited contractile responses in both layers of the bladder. This study presents prostaglandin receptor systems as a potential regulator of urinary bladder contractility. The main contractile effects of PGE₂ in both U&LP and detrusor are mediated via the FP receptor with no observed contribution from any of the four EP receptors.

Comparative-fill urodynamics in individuals with and without detrusor overactivity supports a conceptual model for dynamic elasticity regulation

AIMS

Dynamic elasticity was previously identified in individuals with overactive bladder (OAB) using comparative-fill urodynamics (UD) and is a biomechanical mechanism for acutely regulating detrusor wall tension. On the basis of this data, a conceptual model of dynamic elasticity regulation mediated through a balance of passive mechanisms and active contractions was constructed. The present study tested this model by determining whether individuals with detrusor overactivity (DO) exhibit less dynamic elasticity than individuals without DO.

METHODS

Individuals with and without urgency based on International Consultation on Incontinence Questionnaire-OAB surveys were prospectively enrolled in a comparative-fill UD study. An initial fill defined the presence or absence of DO and determined cystometric capacity. Three additional fills were employed with either passive emptying via a catheter or active voiding. To identify dynamic elasticity, average filling pressures (P_ves ) were compared for fill 1 (before strain softening), fill 2 (after strain softening), and fill 3 (after active void). A dynamic elasticity index was defined.

RESULTS

From 28 participants, those without DO showed decreased P_ves during filling after strain softening and restored P_ves during filling following active voiding, revealing dynamic elasticity. Participants with DO did not show dynamic elasticity. A dynamic elasticity index less than 1.0 cmH₂ O/40% capacity was identified in 2 out of 13 participants without DO and 9 out of 15 with DO, revealing a significant association between DO and reduced/absent dynamic elasticity (P = .024).

CONCLUSIONS

This study supports a conceptual model for dynamic elasticity, a mechanism to acutely regulate detrusor wall tension through a balance of competing active contractile and passive strain mechanisms. Improved understanding of this mechanistic model may help us to identify novel treatment strategies for OAB.

A Preliminary Study on the Impact of Detrusor Overactivity on the Efficacy of Selective Bladder Denervation for the Treatment of Female Refractory Overactive Bladder

OBJECTIVE

To determine whether the presence of detrusor overactivity (DO) is associated with the 12-week and 12-month clinical outcomes of selective bladder denervation (SBD) in women with refractory overactive bladder (OAB).

METHODS

Prospective single institutional study of refractory OAB females who underwent a urodynamic study and were categorized according to DO status (DO- vs DO+) prior to receiving SBD.

RESULTS

Among the 23 patients, 10 were DO- and 13 were DO+. Both groups reported improvement at 12 weeks on the 24-hour pad weight test, in urgency urinary incontinence (UUI) and urgency. At 12 months, both groups still reported improvement in urgency, but only the DO- group reported reduction on the pad weight test and only the DO+ group maintained improvement in the UUI rate. Clinical success (≥50% reduction in UUI) was achieved by all DO- and by 69% of DO+ patients at 12 weeks, and by 60% of DO- and 92% of DO+ patients at 12 months. Treatment benefit (Treatment Benefit Scale ≤2) was reported in 90% of DO- and 85% of DO+ patients at 12 weeks, and in 60% of DO- and 85% of DO+ patients at 12 months. When directly comparing both group outcomes, the only significant difference was the greater reduction of UUI in the DO- group at 12 weeks (-9.0 vs -6.5; P = .045).

CONCLUSION

Refractory OAB females appear to be effectively treated by SBD regardless of baseline DO status. DO status does not seem to be associated with the 12-week and 12-month outcomes of SBD.

Validation of a real-time bladder sensation meter during oral hydration in healthy adults: Repeatability and effects of fill rate and ultrasound probe pressure

OBJECTIVES

A non-invasive protocol was previously developed using three-dimensional ultrasound and a sensation meter to characterize real-time bladder sensation. This study the protocol by measuring the effects of fill rateand ultrasound probe pressure during oral hydration.

METHODS

Healthy volunteers with no urinary symptoms (based on International Consultation on Incontinence Questionnaire on Overactive Bladder surveys) were recruited into an oral hydration study. Throughout two complete fill-void cycles, participants drank 2 L Gatorade G2 (The Gatorade Company, Inc., Chicago, Illinois) and used a touch-screen sensation meter to record real-time bladder sensation (0%-100%). The study was repeated three times, once per week (Visits A, B, and C). In Visits A and B, ultrasound was used to measure bladder volume every 5 minutes. Ultrasound was not used in Visit C except at 100% capacity. Volume data from Visit B were used to estimate volumes throughout the fills in Visit C. Sensation-capacity curves were generated for each fill for comparative analysis.

RESULTS

Ten participants completed three visits (60 total fills). Increased fill rate led to decreased sensation throughout filling, andultrasound probe pressure led to increased sensation. Participants reported higher sensation at low volumes during Fill 1 of Visit A before training with the sensation meter. Sensation curves with intermittent ultrasound showed repeatability for Fill 2 in Visits A and B. Fill rate and ultrasound probe pressure affect real-time bladder sensation during oral hydration.

CONCLUSIONS

This study demonstrated repeatability of real-time bladder sensation during a two-fill oral hydration protocol with ultrasound.

Functional changes in low- and high-threshold afferents in obstruction-induced bladder overactivity

Neural mechanisms of lower urinary tract symptoms in obstruction-induced bladder overactivity remain unclear. We made the first single unit recordings from different types of spinal afferents to determine the effects of bladder outlet obstruction in guinea pigs. A model of gradual bladder outlet obstruction in male guinea pigs was used to produce overactive bladder. Conscious voiding was assessed in metabolic cages, and micturition was recorded in anesthetized guinea pigs in vivo. Single unit extracellular recordings were made ex vivo from spinal afferent nerves in flat sheet preparations of the bladder. Guinea pigs with partially obstructed bladders showed a significant increase in conscious voiding frequency compared with sham-operated guinea pigs. Also, nonvoiding contractions increased significantly in both frequency and amplitude. Although spontaneous firing of low-threshold bladder afferents was increased, their stretch-induced firing was reduced. The proportion of capsaicin-sensitive low-threshold afferents increased in obstructed bladders. Interestingly, spontaneous and stretch-induced firing were both significantly increased in high-threshold afferents after obstruction. In summary, sensory signaling increased in the obstructed bladder during the filling phase. This is largely mediated by low-threshold stretch-sensitive afferents that are activated by increased local nonvoiding contractions. Increased spontaneous firing by high-threshold afferents also contributes. Our findings revealed a complex effect of bladder outlet obstruction on different types of bladder afferents that needs consideration for potential therapeutic targeting of lower urinary tract symptoms in obstruction-induced bladder overactivity.

Investigation of the Syncytial Nature of Detrusor Smooth Muscle as a Determinant of Action Potential Shape

Unlike most excitable cells, certain syncytial smooth muscle cells are known to exhibit spontaneous action potentials of varying shapes and sizes. These differences in shape are observed even in electrophysiological recordings obtained from a single cell. The origin and physiological relevance of this phenomenon are currently unclear. The study presented here aims to test the hypothesis that the syncytial nature of the detrusor smooth muscle tissue contributes to the variations in the action potential profile by influencing the superposition of the passive and active signals. Data extracted from experimental recordings have been compared with those obtained through simulations. The feature correlation studies on action potentials obtained from the experimental recordings suggest the underlying presence of passive signals, called spontaneous excitatory junction potentials (sEJPs). Through simulations, we are able to demonstrate that the syncytial organization of the cells, and the variable superposition of the sEJPs with the "native action potential", contribute to the diversity in the action potential profiles exhibited. It could also be inferred that the fraction of the propagated action potentials is very low in the detrusor. It is proposed that objective measurements of spontaneous action potential profiles can lead to a better understanding of bladder physiology and pathology.

Efficacy and safety of Parecoxib for prevention of catheter-related bladder discomfort in patients undergoing transurethral resection of bladder tumor: Prospective randomised trial

Background and Aims:

Catheter-related bladder discomfort (CRBD) is the urge to void or discomfort in the suprapubic region secondary to an indwelling urinary catheter. We aimed to evaluate the safety and efficacy of single-dose of intravenous parecoxib in reducing the incidence and severity of CRBD in patients undergoing transurethral resection of bladder tumor (TURBT).

Methods:

Sixty-one adult patients, American Society of Anesthesiologists physical status I or II, undergoing elective TURBT under spinal anaesthesia, were randomly allocated to receive 40 mg of IV parecoxib (group P; n = 29) or an equal volume of normal saline (control group C; n = 32). CRBD was graded as none, mild, moderate, and severe. Between-group comparisons were made for the incidence and severity of CRBD, postoperative Visual analog scales (VAS), rescue analgesia equirements, and occurrence of adverse events. Statistical analysis done with the Mann–Whitney U-test and Fisher's Exact Test. A P value of ≤ 0.05 was considered statistically significant.

Results:

Parecoxib significantly reduced the incidence and severity of CRBD at 2, 4, 6, and 12 hours postoperatively compared to placebo (P < 0.05). Median pain VAS scores were lower in the P group at all times except the first hour. Rescue analgesia was given to more patients in group C (16/32, 50%) than in group P (1/29) (P < 0.001). None of the patients who received parecoxib experienced an adverse event.

Conclusion:

A single intravenous injection of parecoxib is safe and effective in decreasing the incidence and severity of CRBD in patients undergoing TURBT.

Trial Registration Identifier:

NCT02729935(www.clinicaltrials.gov).

Overactive Bladder Syndrome: Evaluation and Management

Overactive bladder (OAB) syndrome is a chronic medical condition which has a major influence on the quality of life in a significant amount of the population. OAB affects performance of daily activities and has an estimated prevalence of 16.5%. Many sufferers do not seek medical help. Moreover, many family physicians and even gynecologists are not familiar with this issue. Usually patients suffer from OAB in advanced age. Nocturia is reported as the most bothersome symptom in the elderly population. The aim of our review was to discuss all aspects of this challenging disorder and suggest tools for assessment and management strategies. Practitioners can easily overlook urinary complains if they not directly queried. We would like to encourage practitioners to give more attention to this issue.

Regulation of Spontaneous Contractions in Intact Rat Bladder Strips and the Effects of Hydrogen Peroxide

Enhanced spontaneous contractions are associated with overactive bladder. Elevated levels of reactive oxygen species might contribute to enhanced spontaneous contractions. We investigated the regulation of spontaneous contractions and the effects of hydrogen peroxide (H₂O₂) in intact rat bladder strips. The spontaneous contractions were measured using a tissue bath system. The vehicle or the specific activators/blockers were applied and followed by the application of 0.003 g% H₂O₂. The basal tension, amplitude, and frequency of spontaneous contractions were quantified. Nisoldipine and bisindolylmaleimide 1 had no effects on spontaneous contractions. SKF96365 and Y27632 decreased basal tension and amplitude. Ryanodine slightly increased frequency. Both iberiotoxin and NS-1619 increased amplitude. Apamin reduced frequency but increased amplitude. NS-309 inhibited both the amplitude and frequency. The basal tension and amplitude increased when H₂O₂ was applied. Pretreatment with NS-309 inhibited H₂O₂-elicited augmented amplitude and frequency, while pretreatment with Y-27632 inhibited the augmented basal tension. The combined application of NS-309 and Y27632 almost eliminated spontaneous contractions and its augmentation induced by H₂O₂. In conclusion, Ca²⁺ influx, Rho kinase activation, and SK channel inactivation play important roles in spontaneous contractions in intact bladder strips, whereas only latter two mechanisms may be involved in H₂O₂-elicited increased spontaneous contractions.

Altered expression and modulation of the two-pore-domain (K2P) mechanogated potassium channel TREK-1 in overactive human detrusor

Detrusor overactivity (DO) is the abnormal response of the urinary bladder to physiological stretch during the filling phase of the micturition cycle. The mechanisms of bladder smooth muscle compliance upon the wall stretch are poorly understood. We previously reported that the function of normal detrusor is regulated by TREK-1, a member of the mechanogated subfamily of two-pore-domain potassium (K_2P) channels. In the present study, we aimed to identify the changes in expression and function of TREK-1 channels under pathological conditions associated with DO, evaluate the potential relationship between TREK-1 channels and cytoskeletal proteins in the human bladder, and test the possibility of modulation of TREK-1 channel expression by small RNAs. Expression of TREK-1 channels in DO specimens was 2.7-fold decreased compared with control bladders and was associated with a significant reduction of the recorded TREK-1 currents. Isolated DO muscle strips failed to relax when exposed to a TREK-1 channel opener. Immunocytochemical labeling revealed close association of TREK-1 channels with cell cytoskeletal proteins and caveolins, with caveolae microdomains being severely disrupted in DO specimens. Small activating RNA (saRNA) tested in vitro provided evidence that expression of TREK-1 protein could be partially upregulated. Our data confirmed a significant downregulation of TREK-1 expression in human DO specimens and provided evidence of close association between the channel, cell cytoskeleton, and caveolins. Upregulation of TREK-1 expression by saRNA could be a future step for the development of in vivo pharmacological and genetic approaches to treat DO in humans.

Incidence and risk factors of recurrence of overactive bladder symptoms after discontinuation of successful medical treatment

Purpose

To identify incidence and risk factors of recurrence after discontinuation of successful antimuscarinic therapy in patients with overactive bladder (OAB).

Materials and Methods

This was a prospective, multicenter trial. Patients who had antimuscarinic agents for more than 12 weeks and showed successful response were enrolled. Successful response was defined as answering 'benefit' for patient perception of treatment benefit and answer lesser than 3 points in patient's perception of bladder condition (PPBC). The enrolled patients discontinued the antimuscarinics, and we evaluated their recurrence with PPBC and OAB symptom score (OABSS) at 1, 3, 6, and 12 months. Primary purpose was to identify the recurrence rate and secondary purpose was to reveal risk factors.

Results

Four hundred forty-one patients enrolled and 371 patients completed 6-month follow-up. The enrolled patients showed 1.6 points in PPBC, 2.9 points in OABSS and 1.4 points in IPSS (quality of life) which represented successful response after using antimuscarinics. The cumulative rates of recurrence were 25.6%, 42.3%, and 52.2% at 1, 3, 6 months, respectively. Among 177 patients who did not show recurrence at 6 months, 41 patients were followed up and 4 patients of the 41 patients (9.7%) showed recurrence at 12 months. On univariate and multivariate analyses of recurrence, OAB wet was the risk factor for recurrence after 6 months of discontinuation.

Conclusions

Discontinuation of antimuscarinic therapy after successful treatment resulted in high recurrence rate with time and OAB wet was the independent risk factor for recurrence.

Efficacy and Safety of Initial Combination Treatment of an Alpha Blocker with an Anticholinergic Medication in Benign Prostatic Hyperplasia Patients with Lower Urinary Tract Symptoms: Updated Meta-Analysis

BACKGROUND

There is still controversy as to whether initial combination treatment is superior to serial addition of anticholinergics after maintenance or induction of alpha blockers in benign prostatic hyperplasia (BPH)/lower urinary tract symptoms (LUTS).

OBJECTIVE

The objective of this study was to determine the benefits and safety of initial combination treatment of an alpha blocker with anticholinergic medication in BPH/LUTS through a systematic review and meta-analysis.

METHODS

We conducted a meta-analysis of improvement in LUTS using International Prostate Symptom Score (IPSS), maximal urinary flow rate (Qmax), post-voided residual volume (PVR), and quality of life (QoL).

RESULTS

In total, 16 studies were included in our analysis, with a total sample size of 3,548 subjects (2,195 experimental subjects and 1,353 controls). The mean change in total IPSS improvement from baseline in the combination group versus the alpha blocker monotherapy group was -0.03 (95% CI: -0.14-0.08). The pooled overall SMD change of storage IPSS improvement from baseline was -0.28 (95% CI: -0.40 - -0.17). The pooled overall SMD changes of QoL, Qmax, and PVR were -0.29 (95% CI: -0.50 - -0.07), 0.00 (95% CI: -0.08-0.08), and 0.56 (95% CI: 0.23-0.89), respectively. There was no significant difference in the number of acute urinary retention (AUR) events or PVR.

CONCLUSIONS

Initial combination treatment of an alpha blocker with anticholinergic medication is efficacious for in BPH/ LUTS with improved measures such as storage symptoms and QoL without causing significant deterioration of voiding 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.

Fundamentals and clinical perspective of urethral sphincter instability as a contributing factor in patients with lower urinary tract dysfunction--ICI-RS 2014

Aims

Urethral pathophysiology is often neglected in discussions of bladder dysfunction. It has been debated whether “urethral sphincter instability,” referred to based on observed “urethral pressure variations,” is an important aspect of overactive bladder syndrome (OAB). The purpose of this report is to summarize current urethral pathophysiology evidence and outline directions for future research based on a literature review and discussions during the ICI‐RS meeting in Bristol in 2014.

Methods

Urethral pathophysiology with a focus on urethral pressure variation (UPV) was presented and discussed in a multidisciplinary think tank session at the ICI_R meeting in Bristol 2014. This think tank session was based on collaboration between physicians and basic science researchers.

Results

Experimental animal studies or studies performed in clinical series (predominantly symptomatic women) provided insights into UPV, but the findings were inconsistent and incomplete. However, UPV is certainly associated with lower urinary tract symptoms (likely OAB), and thus, future research on this topic is relevant.

Conclusions

Future research based on adequately defined clinical (and urodynamic) parameters with precisely defined patient groups might shed better light on the cause of OAB symptoms. Further fundamental investigation of urethral epithelial–neural interactions via the release of mediators should enhance our knowledge and improve the management of patients with OAB. Neurourol. Urodynam. 35:318–323, 2016. © 2016 The Authors. Neurourology and Urodynamics published by Wiley Periodicals, Inc.

Original Research: Combined model of bladder detrusor smooth muscle and interstitial cells

Although patients with lower urinary tract symptoms constitute a large and still growing population, understanding of bladder detrusor muscle physiology remains limited. Understanding the interactions between the detrusor smooth muscle cells and other bladder cell types (e.g. interstitial cells, IC) that may significantly contribute to coordinating and modulating detrusor contractions represents a considerable challenge. Computer modeling could help to elucidate some properties that are difficult to address experimentally; therefore, we developed in silico models of detrusor smooth muscle cell and interstitial cells, coupled through gap junctions. The models include all of the major ion conductances and transporters described in smooth muscle cell and interstitial cells in the literature. The model of normal detrusor muscle (smooth muscle cell and interstitial cells coupled through gap junctions) completely reproduced the experimental results obtained with detrusor strips in the presence of several pharmacological interventions (ryanodine, caffeine, nimodipine), whereas the model of smooth muscle cell alone (without interstitial cells) failed to reproduce the experimental results. Next, a model of overactive bladder, a highly prevalent clinical condition in both men and women with increasing incidence at older ages, was produced by modifying several processes as reported previously: a reduction of Ca(2+)-release through ryanodine receptors and a reduction of Ca(2+)-dependent K(+)-conductance with augmented gap junctional coupling. This model was also able to reproduce the pharmacological modulation of overactive bladder. In conclusion, a model of bladder detrusor muscle was developed that reproduced experimental results obtained in both normal and overactive bladder preparations. The results indicate that the non-smooth muscle cells of the detrusor (interstitial cells) contribute significantly to the contractile behavior of bladder detrusor muscle and should not be neglected. The model suggests that reduced Ca(2+)-release through ryanodine receptors and Ca(2+)-dependent K(+)-conductance together with augmented gap junctional coupling might play a major role in overactive bladder pathogenesis.

Structural and functional changes in gap junctional intercellular communication in a rat model of overactive bladder syndrome induced by partial bladder outlet obstruction

The aim of the present study was to investigate the association between connexin (Cx)43 levels and alterations in gap junctional mediation of intercellular communication in overactive bladder syndrome (OAB), and to examine the effects of connexin inhibitor on this condition. Adult female Wistar rats with OAB following partial bladder outlet obstruction (PBBO) (OAB group, n=37) and sham-operated rats (control group, n=17) were studied. The ultrastructure of the rat detrusor was observed by transmission electron microscopy and the protein expression levels of Cx43 were analyzed using western blot analysis. Furthermore, bladder detrusor cells in both groups were cultured and cells in the OAB group were randomly divided into ten groups. In nine of these groups, 18-β glycyrrhetinic acid (18β-GA) was administered at various doses and durations. All groups were compared using fluorescence redistribution after photobleaching and a laser scanning confocal microscope. Cystometry demonstrated that gap junctions were an abundant mechanism among adjacent cells, and Cx43 protein expression levels were increased in the OAB group following 6 weeks of obstruction, as compared with the control group. Mean fluorescence recovery rates in the OAB group were significantly increased, as compared with the control group (P<0.01). Mean fluorescence recovery rates were noted following 18β-GA administration. These results suggested that upregulation of Cx43 induces structural and functional alterations in gap junctional intercellular communication following PBOO, and connexin inhibitors may be a novel therapeutic strategy for the clinical treatment of OAB.

β3-Adrenoceptor agonists for overactive bladder syndrome: Role of translational pharmacology in a repositioning clinical drug development project

β3-Adrenoceptor agonists were originally considered as a promising drug class for the treatment of obesity and/or type 2 diabetes. When these development efforts failed, they were repositioned for the treatment of the overactive bladder syndrome. Based on the example of the β3-adrenoceptor agonist mirabegron, but also taking into consideration evidence obtained with ritobegron and solabegron, we discuss challenges facing a translational pharmacology program accompanying clinical drug development for a first-in-class molecule. Challenges included generic ones such as ligand selectivity, species differences and drug target gene polymorphisms. Challenges that are more specific included changing concepts of the underlying pathophysiology of the target condition while clinical development was under way; moreover, a paucity of public domain tools for the study of the drug target and aspects of receptor agonists as drugs had to be addressed. Nonetheless, a successful first-in-class launch was accomplished. Looking back at this translational pharmacology program, we conclude that a specifically tailored and highly flexible approach is required. However, several of the lessons learned may also be applicable to translational pharmacology programs in other indications.

Spontaneous Contractile Activity of the Detrusor Muscle and Its Role in the Pathogenesis of Overactive Bladder Syndrome

There is accumulated evidence that spontaneous contractions (SCs) in the bladder wall are associated with afferent nerve firing in the bladder. The role of the urothelium in bladder sensation might be restricted to pathological conditions, such as interstitial cystitis or chemical cystitis in which the release of urothelium-derived mediators such as adenosine triphosphate is increased. Recent publications imply that SCs in bladders with detrusor overactivity due to spinal cord injury or bladder outlet obstruction are modulated by intracellular signal transduction mechanisms such as the RhoA/Rho-kinase pathway, denervation-supersensitivity to acetylcholine, changes in ion channel activity, enhanced gap-junctional intercellular communication, alterations in interstitial cells of Cajal, the actions of local mediators in the detrusor and the influence of the urothelium. Spontaneous contractions and possible consequent afferent nerve firing might participate in the generation of overactive bladder syndrome.

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

BACKGROUND

Protein kinase C (PKC) is expressed in many tissues and organs including the urinary bladder, however, its role in bladder physiology and pathophysiology is still evolving. The aim of this review was to evaluate available evidence on the involvement of PKC in regulation of detrusor contractility, muscle tone of the bladder wall, spontaneous contractile activity and bladder function under physiological and pathophysiological conditions.

METHODS

This is a non-systematic review of the published literature which summarizes the available animal and human data on the role of PKC signaling in the urinary bladder under different physiological and pathophysiological conditions. A wide PubMed search was performed including the combination of the following keywords: "urinary bladder", "PKC", "detrusor contractility", "bladder smooth muscle", "detrusor relaxation", "peak force", "detrusor underactivity", "partial bladder outlet obstruction", "voltage-gated channels", "bladder nerves", "PKC inhibitors", "PKC activators". Retrieved articles were individually screened for the relevance to the topic of this review with 91 citations being selected and included in the data analysis.

DISCUSSION

Urinary bladder function includes the ability to store urine at low intravesical pressure followed by a subsequent release of bladder contents due to a rapid phasic contraction that is maintained long enough to ensure complete emptying. This review summarizes the current concepts regarding the potential contribution of PKC to contractility, physiological voiding, and related signaling mechanisms involved in the control of both the storage and emptying phases of the micturition cycle, and in dysfunctional voiding. Previous studies linked PKC activation exclusively with an increase in generation of the peak force of smooth muscle contraction, and maximum force generation in the lower urinary tract. More recent data suggests that PKC presents a broader range of effects on urinary bladder function including regulation of storage, emptying, excitability of the detrusor, and bladder innervation. In this review, we evaluated the mechanisms of peripheral and local regulation of PKC signaling in the urinary bladder, and their impact on different phases of the micturition cycle under physiological and pathophysiological conditions.

Tamsulosin combined with solifenacin versus tamsulosin monotherapy for male lower urinary tract symptoms: a meta-analysis

OBJECTIVE

To evaluate the efficacy and safety of tamsulosin and solifenacin combination therapy compared with tamsulosin monotherapy for male lower urinary tract symptoms (LUTS).

METHODS

We identified all eligible studies that compared tamsulosin and solifenacin combination therapy with tamsulosin monotherapy for male LUTS (up to January 2015). The fixed- or random-effects model was selected depending on the proportion of heterogeneity.

RESULTS

Seven articles were identified as eligible for this meta-analysis, with a total of 3063 participants. Synthetic data showed combination therapy had significant improvements in Storage International Prostate Symptom Score (WMD = -0.60; 95% CI: -0.81 to -0.38, P < 0.0001), quality of life (WMD = -0.23; 95% CI: -0.34 to -0.11, P < 0.0001), micturitions per 24 hours (WMD = -0.70; 95% CI: -0.86 to -0.55, P < 0.0001) and urgency episodes per 24 hours (WMD = -0.26; 95% CI: -0.48 to -0.05, P = 0.018). The incidence of adverse effects in the tamsulosin and solifenacin combined therapy group (30.82%) was similar to the tamsulosin monotherapy group (25.75%). Acute urinary retention was seldom reported in the studies and no clinically significant changes regarding Qmax were showed in our meta-analysis.

CONCLUSIONS

Tamsulosin and solifenacin combination therapy may be a reasonable option for male LUTS patients, especially for those who have significant storage symptoms. However, PVR should be measured during treatment to assess the increase in PVR or the incidence of AUR.

Management of Catheter-Related Bladder Discomfort in Patients Who Underwent Elective Surgery

OBJECTIVE

Despite the various treatment and prevention options for catheter-related bladder discomfort (CRBD), many uncertainties persist in clinical practice. To systematically review the literature on the management of CRBD in patients who underwent surgery.

MATERIALS AND METHODS

Eligible, randomized controlled trials were identified from electronic databases (Cochrane Central Register of Controlled Trials, Medline, and EMBASE) without language restrictions. Selection criteria, methodological rigor, and risk of bias were evaluated by two independent reviewers using Cochrane Collaboration's tools.

RESULTS

A total of 1441 patients from 14 articles published between 2005 and 2014 were included. Data heterogeneity precluded meta-analysis; therefore, data were synthesized narratively. Compared with nonurological surgery, CRBD is frequent and occurred immediately after urological surgery, especially after transurethral resection of the bladder tumor (TURBT). Data from included studies suggested that muscarinic antagonists, anesthetics, antiepileptics, and analgesics were associated with significant improvement in symptoms and reducing the incidence of CRBD, compared with placebo. Anticholinergic agents and antiepileptics (gabapentin and pregabalin) administered 1 hour before surgery reduced the incidence and severity of CRBD in the immediate postoperative period. Tramadol and ketamine are centrally acting opioid analgesics with antimuscarinic actions, which effectively prevent CRBD when administered intravenously. Paracetamol administered was also effective for the management of CRBD. Additionally, we perceived that TURBT is the surgical procedure that is the most refractory to treatment.

CONCLUSIONS

Muscarinic antagonists, anesthetics, antiepileptics, and paracetamol appear to achieve the greatest improvement in the clinical symptoms and a significant reduction in the incidence of CRBD compared with placebo. Although these studies observed a high incidence of intervention-related side effects, in general, patients tolerated these treatments well.

Hydrogen sulfide plays a key role in the inhibitory neurotransmission to the pig intravesical ureter

According to previous observations nitric oxide (NO), as well as an unknown nature mediator are involved in the inhibitory neurotransmission to the intravesical ureter. This study investigates the hydrogen sulfide (H₂S) role in the neurogenic relaxation of the pig intravesical ureter. We have performed western blot and immunohistochemistry to study the expression of the H₂S synthesis enzymes cystathionine γ-lyase (CSE) and cystathionine β-synthase (CBS), measurement of enzymatic production of H₂S and myographic studies for isometric force recording. Immunohistochemical assays showed a high CSE expression in the intravesical ureter muscular layer, as well as a strong CSE-immunoreactivity within nerve fibres distributed along smooth muscle bundles. CBS expression, however, was not consistently observed. On ureteral strips precontracted with thromboxane A₂ analogue U46619, electrical field stimulation (EFS) and the H₂S donor P-(4-methoxyphenyl)-P-4-morpholinylphosphinodithioic acid (GYY4137) evoked frequency- and concentration-dependent relaxations. CSE inhibition with DL-propargylglycine (PPG) reduced EFS-elicited responses and a combined blockade of both CSE and NO synthase (NOS) with, respectively, PPG and N^G-nitro-L-arginine (L-NOARG), greatly reduced such relaxations. Endogenous H₂S production rate was reduced by PPG, rescued by addition of GYY4137 and was not changed by L-NOARG. EFS and GYY4137 relaxations were also reduced by capsaicin-sensitive primary afferents (CSPA) desensitization with capsaicin and blockade of ATP-dependent K⁺ (K_ATP) channels, transient receptor potential A1 (TRPA₁), transient receptor potential vanilloid 1 (TRPV₁), vasoactive intestinal peptide/pituitary adenylyl cyclase-activating polypeptide (VIP/PACAP) and calcitonin gene-related peptide (CGRP) receptors with glibenclamide, HC030031, AMG9810, PACAP_6–38 and CGRP_8–37, respectively. These results suggest that H₂S, synthesized by CSE, is involved in the inhibitory neurotransmission to the pig intravesical ureter, through an NO-independent pathway, producing smooth muscle relaxation via K_ATP channel activation. H₂S also promotes the release of inhibitory neuropeptides, as PACAP 38 and/or CGRP from CSPA through TRPA₁, TRPV₁ and related ion channel activation.

Pre- and post-junctional bradykinin B2 receptors regulate smooth muscle tension to the pig intravesical ureter

AIMS

Neuronal and non-neuronal bradykinin (BK) receptors regulate the contractility of the bladder urine outflow region. The current study investigates the role of BK receptors in the regulation of the smooth muscle contractility of the pig intravesical ureter.

METHODS

Western blot and immunohistochemistry were used to show the expression of BK B1 and B2 receptors and myographs for isometric force recordings.

RESULTS

B2 receptor expression was consistently detected in the intravesical ureter urothelium and smooth muscle layer, B1 expression was not detected where a strong B2 immunoreactivity was observed within nerve fibers among smooth muscle bundles. On ureteral strips basal tone, BK induced concentration-dependent contractions, were potently reduced by extracellular Ca(2+) removal and by B2 receptor and voltage-gated Ca(2+) (VOC) channel blockade. BK contraction did not change as a consequence of urothelium mechanical removal or cyclooxygenase and Rho-associated protein kinase inhibition. On 9,11-dideoxy-9a,11a-methanoepoxy prostaglandin F2α (U46619)-precontracted samples, under non-adrenergic non-cholinergic (NANC) and nitric oxide (NO)-independent NANC conditions, electrical field stimulation-elicited frequency-dependent relaxations which were reduced by B2 receptor blockade. Kallidin, a B1 receptor agonist, failed to increase preparation basal tension or to induce relaxation on U46619-induced tone.

CONCLUSIONS

The present results suggest that BK produces contraction of pig intravesical ureter via smooth muscle B2 receptors coupled to extracellular Ca(2+) entry mainly via VOC (L-type) channels. Facilitatory neuronal B2 receptors modulating NO-dependent or independent NANC inhibitory neurotransmission are also demonstrated.

BK channel activators and their therapeutic perspectives

The large conductance calcium- and voltage-activated K⁺ channel (KCa1.1, BK, MaxiK) is ubiquitously expressed in the body, and holds the ability to integrate changes in intracellular calcium and membrane potential. This makes the BK channel an important negative feedback system linking increases in intracellular calcium to outward hyperpolarizing potassium currents. Consequently, the channel has many important physiological roles including regulation of smooth muscle tone, neurotransmitter release and neuronal excitability. Additionally, cardioprotective roles have been revealed in recent years. After a short introduction to the structure, function and regulation of BK channels, we review the small organic molecules activating BK channels and how these tool compounds have helped delineate the roles of BK channels in health and disease.

Pathophysiology and animal modeling of underactive bladder

While the symptomology of underactive bladder (UAB) may imply a primary dysfunction of the detrusor muscle, insights into pathophysiology indicate that both myogenic and neurogenic mechanisms need to be considered. Due to lack of proper animal models, the current understanding of the UAB pathophysiology is limited, and much of what is known about the clinical etiology of the condition has been derived from epidemiological data. We hereby review current state of the art in the understanding of the pathophysiology of and animal models used to study the UAB.

Therapeutic modulation of urinary bladder function: multiple targets at multiple levels

Storage dysfunction of the urinary bladder, specifically overactive bladder syndrome, is a condition that occurs frequently in the general population. Historically, pathophysiological and treatment concepts related to overactive bladder have focused on smooth muscle cells. Although these are the central effector, numerous anatomic structures are involved in their regulation, including the urothelium, afferent and efferent nerves, and the central nervous system. Each of these structures involves receptors for—and the urothelium itself also releases—many mediators. Moreover, hypoperfusion, hypertrophy, and fibrosis can affect bladder function. Established treatments such as muscarinic antagonists, β-adrenoceptor agonists, and onabotulinumtoxinA each work in part through their effects on the urothelium and afferent nerves, as do α1-adrenoceptor antagonists in the treatment of voiding dysfunction associated with benign prostatic hyperplasia; however, none of these treatments are specifically targeted to the urothelium and afferent nerves. It remains to be explored whether future treatments that specifically act at one of these structures will provide a therapeutic advantage.

Bladder smooth muscle strip contractility as a method to evaluate lower urinary tract pharmacology

We describe an in vitro method to measure bladder smooth muscle contractility, and its use for investigating physiological and pharmacological properties of the smooth muscle as well as changes induced by pathology. This method provides critical information for understanding bladder function while overcoming major methodological difficulties encountered in in vivo experiments, such as surgical and pharmacological manipulations that affect stability and survival of the preparations, the use of human tissue, and/or the use of expensive chemicals. It also provides a way to investigate the properties of each bladder component (i.e. smooth muscle, mucosa, nerves) in healthy and pathological conditions. The urinary bladder is removed from an anesthetized animal, placed in Krebs solution and cut into strips. Strips are placed into a chamber filled with warm Krebs solution. One end is attached to an isometric tension transducer to measure contraction force, the other end is attached to a fixed rod. Tissue is stimulated by directly adding compounds to the bath or by electric field stimulation electrodes that activate nerves, similar to triggering bladder contractions in vivo. We demonstrate the use of this method to evaluate spontaneous smooth muscle contractility during development and after an experimental spinal cord injury, the nature of neurotransmission (transmitters and receptors involved), factors involved in modulation of smooth muscle activity, the role of individual bladder components, and species and organ differences in response to pharmacological agents. Additionally, it could be used for investigating intracellular pathways involved in contraction and/or relaxation of the smooth muscle, drug structure-activity relationships and evaluation of transmitter release. The in vitro smooth muscle contractility method has been used extensively for over 50 years, and has provided data that significantly contributed to our understanding of bladder function as well as to pharmaceutical development of compounds currently used clinically for bladder management.

NS19504: a novel BK channel activator with relaxing effect on bladder smooth muscle spontaneous phasic contractions

Large-conductance Ca(2+)-activated K(+) channels (BK, KCa1.1, MaxiK) are important regulators of urinary bladder function and may be an attractive therapeutic target in bladder disorders. In this study, we established a high-throughput fluorometric imaging plate reader-based screening assay for BK channel activators and identified a small-molecule positive modulator, NS19504 (5-[(4-bromophenyl)methyl]-1,3-thiazol-2-amine), which activated the BK channel with an EC50 value of 11.0 ± 1.4 µM. Hit validation was performed using high-throughput electrophysiology (QPatch), and further characterization was achieved in manual whole-cell and inside-out patch-clamp studies in human embryonic kidney 293 cells expressing hBK channels: NS19504 caused distinct activation from a concentration of 0.3 and 10 µM NS19504 left-shifted the voltage activation curve by 60 mV. Furthermore, whole-cell recording showed that NS19504 activated BK channels in native smooth muscle cells from guinea pig urinary bladder. In guinea pig urinary bladder strips, NS19504 (1 µM) reduced spontaneous phasic contractions, an effect that was significantly inhibited by the specific BK channel blocker iberiotoxin. In contrast, NS19504 (1 µM) only modestly inhibited nerve-evoked contractions and had no effect on contractions induced by a high K(+) concentration consistent with a K(+) channel-mediated action. Collectively, these results show that NS19504 is a positive modulator of BK channels and provide support for the role of BK channels in urinary bladder function. The pharmacologic profile of NS19504 indicates that this compound may have the potential to reduce nonvoiding contractions associated with spontaneous bladder overactivity while having a minimal effect on normal voiding.

Response of the human detrusor to stretch is regulated by TREK-1, a two-pore-domain (K2P) mechano-gated potassium channel

The mechanisms of mechanosensitivity underlying the response of the human bladder to stretch are poorly understood. Animal data suggest that stretch-activated two-pore-domain (K2P) K(+) channels play a critical role in bladder relaxation during the filling phase. The objective of this study was to characterize the expression and function of stretch-activated K2P channels in the human bladder and to clarify their physiological role in bladder mechanosensitivity. Gene and protein analysis of the K2P channels TREK-1, TREK-2 and TRAAK in the human bladder revealed that TREK-1 is the predominantly expressed member of the mechano-gated subfamily of K2P channels. Immunohistochemical labelling of bladder wall identified higher levels of expression of TREK-1 in detrusor smooth muscle cells in comparison to bladder mucosa. Functional characterization and biophysical properties of the predominantly expressed member of the K2P family, the TREK-1 channel, were evaluated by in vitro organ bath studies and the patch-clamp technique. Electrophysiological recordings from single smooth muscle cells confirmed direct activation of TREK-1 channels by mechanical stretch and negative pressure applied to the cell membrane. Inhibition of TREK-1 channels in the human detrusor significantly delayed relaxation of the stretched bladder smooth muscle strips and triggered small-amplitude spontaneous contractions. Application of negative pressure to cell-attached patches (-20 mmHg) caused a 19-fold increase in the open probability (NPo) of human TREK-1 channels. l-Methionine (1 mm), a specific TREK-1 inhibitor, dramatically decreased the NPo of TREK-1 channels from 0.045 ± 0.003 to 0.008 ± 0.001 (n = 8, P ≤ 0.01). Subsequent addition of arachidonic acid (10 μm), a channel opener, increased the open probability of methionine-inhibited unitary currents up to 0.43 ± 0.05 at 0 mV (n = 9, P ≤ 0.05). The results of our study provide direct evidence that the response of the human detrusor to mechanical stretch is regulated by activation of mechano-gated TREK-1 channels. Impaired mechanosensation and mechanotransduction associated with the changes in stretch-activated K2P channels may underlie myogenic bladder dysfunction in humans.

Effect of intraoperative paracetamol on catheter-related bladder discomfort: a prospective, randomized, double-blind study

BACKGROUND

The insertion of urinary catheters during urinary surgical interventions may lead to catheter-related bladder discomfort (CRBD) in the postoperative period.

OBJECTIVE

We aimed to evaluate the effect of single-dose intravenous paracetamol on CRBD.

METHODS

In this randomized, controlled, double-blind study, 64 patients (age >18 years, American Society of Anesthesiologists Physical Status I-II) requiring urinary bladder catheterization for percutaneous nephrolithotomy were assigned to groups that received either intravenous paracetamol (15 mg/kg) (group P) or NaCl 0.9% solution (control group [group C]) 30 minutes before the end of surgery. Patients received patient-controlled analgesia (10-mg bolus of meperidine, without infusion, 20-minute lock out) postoperatively. CRBD and pain status were assessed at 30 minutes and 1, 2, 4, 6, and 12 hours postoperatively. Postoperative meperidine requirement and patient and surgeon satisfaction were assessed.

RESULTS

Group P had significantly lower CRBD scores at all time points except at 12 hours postoperatively compared with group C (P < 0.05). Total meperidine consumption was significantly higher in group C (P < 0.05). Patient and surgeon satisfaction scores were significantly higher in group P (P < 0.05).

CONCLUSIONS

Intraoperative single-dose paracetamol was found to be effective in reducing the severity of CRBD and pain in urologic surgery. We suggest that it may be an efficient, reliable, easy-to-apply drug for CRBD. ClinicalTrials.gov identifier: NCT01652183.

Cajal-like interstitial cells as a novel target in detrusor overactivity treatment: true or myth?

Introduction

The Cajal–like intestitial cells (ICCs) act as a pacemaker and are responsible for generating smooth muscle activity in the gastrointestinal tract (GI). Interstitial cells that resemble ICCs in the GI have been identified in the urinary bladder.

Materials and methods

This review is based on a systemic literature research. The medline/pubmed, scopus, embase, and Web of Science databases were browsed in order to identify original and review articles, as well as editorials relating to cajal–like cells, urinary bladder, detrusor overactivity, overactive bladder, glivec, etc. The controlled vocabulary of the Medical Subject Headings (MeSH) database was used to ensure the sensitivity of the searches. 40 papers met the criteria and were used for this review.

Results

Cajal cells lie in close proximity to the muscle cells, autonomic nerve endings, and urothelial cells. There is increasing evidence that ICCs play role in urinary tract dysfunction development (e.g. detrusor overactivity, primary obstructive megaureter, congenital ureteropelvic junction obstruction, etc.). ICCs may be responsible for generating electrical potentials and induction of detrusor muscle contractions. Novel pathomechanisms of detrusor overactivity development have been postulated, as follows: 1) the disturbance of spontaneous contractility caused by altered signal transduction of ICCs between nerves and detrusor muscle cells, and 2). the alteration in signal transduction between urothelium and afferent nerve endings via suburothelial ICCs. The c–kit receptor is not only a detection marker of these cells, but may also play a crucial role in the control of bladder function.

Conclusions

Cajal cells in urinary bladder suggest that the c–kit receptor may provide a novel target for treating detrusor overactivity. The review presents the current knowledge of ICCs, its role in urinary bladder function, and potential novel therapeutic strategy.