Basic Mechanisms of Urgency: Preclinical and Clinical Evidence

Impact of intravascular hemolysis on functional and molecular alterations in the urinary bladder: implications for an overactive bladder in sickle cell disease

Patients with sickle cell disease (SCD) display an overactive bladder (OAB). Intravascular hemolysis in SCD is associated with various severe SCD complications. However, no experimental studies have evaluated the effect of intravascular hemolysis on bladder function. This study aimed to assess the effects of intravascular hemolysis on the micturition process and the contractile mechanisms of the detrusor smooth muscle (DSM) in a mouse model with phenylhydrazine (PHZ)-induced hemolysis; furthermore, it aimed to investigate the role of intravascular hemolysis in the dysfunction of nitric oxide (NO) signaling and in increasing oxidative stress in the bladder. Mice underwent a void spot assay, and DSM contractions were evaluated in organ baths. The PHZ group exhibited increased urinary frequency and increased void volumes. DSM contractile responses to carbachol, KCl, α-β-methylene-ATP, and EFS were increased in the PHZ group. Protein expression of phosphorylated endothelial NO synthase (eNOS) (Ser-1177), phosphorylated neuronal NO synthase (nNOS) (Ser-1417), and phosphorylated vasodilator-stimulated phosphoprotein (VASP) (Ser-239) decreased in the bladder of the PHZ group. Protein expression of oxidative stress markers, NOX-2, 3-NT, and 4-HNE, increased in the bladder of the PHZ group. Our study shows that intravascular hemolysis promotes voiding dysfunction correlated with alterations in the NO signaling pathway in the bladder, as evidenced by reduced levels of p-eNOS (Ser-1177), nNOS (Ser-1417), and p-VASP (Ser-239). The study also showed that intravascular hemolysis increases oxidative stress in the bladder. Our study indicates that intravascular hemolysis promotes an OAB phenotype similar to those observed in patients and mice with SCD.

Effects of a new selective β3 -adrenoceptor agonist, vibegron, on bladder and urethral function in a rat model of Parkinson's disease

OBJECTIVES

Parkinson's disease caused by the loss of dopaminergic neurons induces not only motor dysfunction but also lower urinary tract dysfunction. Patients with Parkinson's disease have recently been reported to experience both urge urinary incontinence (overactive bladder) and stress urinary incontinence, the latter of which occurs when the pressure of the bladder exceeds that of the urethra. Vibegron is a highly selective novel β3 -adrenoceptor agonist approved for the treatment of overactive bladder. However, how β3 -adrenoceptor agonists affect urethral function remains unclear. In a clinical report, the urethral function of patients with Parkinson's disease was shown to be degraded. The present study aimed to investigate the effects of vibegron on lower urinary tract activity in a rat model of Parkinson's disease.

METHODS

In a rat model of Parkinson's disease induced by unilateral 6-hydroxydopamine injection into the substantia nigra pars compacta, we examined the effects of vibegron on bladder and urethral activity.

RESULTS

Cystometric analysis revealed that, compared with vehicle injection, intravenous injection of 3 mg/kg vibegron significantly increased the inter-contraction interval (p < .05) and reduced voiding pressure (p < .01). However, no significant effects on urethral function were observed.

CONCLUSIONS

The results of the present study provide corroborating evidence that bladder dysfunction is suppressed by the administration of vibegron in Parkinson's disease model rats, confirming that vibegron is effective for treating overactive bladder without further worsening urethral function. These findings may contribute to a better understanding of the mechanisms of β3 -adrenoceptor agonists.

Updates of Overactive Bladder in Pediatrics

Overactive bladder (OAB) is clinically defined as urinary urgency with or without urinary incontinence. It is associated with daytime frequency or constipation and has a prevalence of approximately 5%-12% among 5- to 10-year-olds. The appropriate functional exchange between the pontine micturition center, periaqueductal gray matter, and prefrontal cortex is important for proper micturition control. Several studies on pediatric cases observed a link between OAB and neuropsychiatric problems, such as anxiety, depression, and attention deficit, and treatment of these comorbidities improved patient symptoms. In this review, we present the pathophysiology of OAB, its associated conditions, and aspects related to updates in OAB treatment, and we propose a step-by-step treatment approach following this sequence: behavioral therapy, medical treatment, and invasive treatment. Although anticholinergic drugs are the mainstay of OAB medical treatment, beta-3 agonists and alpha-blockers are now recommended as a result of significant advancements in pharmacologic treatment in the last 10 years. Electrical stimulation techniques and botulinum toxin are also effective and can be used, especially in conventional treatment-refractory cases.

Moxibustion attenuates neurogenic detrusor overactivity in spinal cord injury rats by inhibiting M2/ATP/P2X3 pathway

PURPOSE

Activation of muscarinic receptors located in bladder sensory pathways is generally considered to be the primary contributor for driving the pathogenesis of neurogenic detrusor overactivity following spinal cord injury. The present study is undertaken to examine whether moxibustion improves neurogenic detrusor overactivity via modulating the abnormal muscarinic receptor pathway.

MATERIALS AND METHODS

Female Sprague-Dawley rats were subjected to spinal cord injury with T9-10 spinal cord transection. Fourteen days later, animals were received moxibustion treatment for one week. Urodynamic parameters and pelvic afferents discharge were measured. Adenosine triphosphate (ATP) content in the voided cystometry fluid was determined. Expressions of M2, M3, and P2X3 receptors in the bladder mucosa were evaluated.

RESULTS

Moxibustion treatment prevented the development of detrusor overactivity in spinal cord injury rats, with an increase in the intercontraction interval and micturition pressure threshold and a decrease in afferent activity during filling. The expression of M2 was markedly suppressed by moxibustion, accompanied by a reduction in the levels of ATP and P2X3. M2 receptor antagonist methoctramine hemihydrate had similar effects to moxibustion on bladder function and afferent activity, while the M2-preferential agonist oxotremorine methiodide abolished the beneficial effects of moxibustion.

CONCLUSION

Moxibustion is a potential candidate for treating neurogenic bladder overactivity in a rat model of spinal cord injury, possibly through inhibiting the M2/ATP/P2X3 pathway.

Problems with enuresis management-A personal view

Much has happened since the end of the era when enuresis was blamed on the parents or the children themselves. Still, there are large gaps in our knowledge and large parts of modern enuresis management guidelines are (still) not based on firm evidence. In this review I will question the following commonly made assumptions regarding enuresis evaluation and treatment: •It is important to subdivide enuresis according to the presence of daytime symptoms•Voiding charts are crucial in the primary evaluation of the enuretic child•All children with enuresis need to be screened for behavioral or psychiatric issues•Concomittant daytime incontinence needs to be successfully treated before addressing the enuresis•Concomittant constipation needs to be successfully treated before addressing the enuresis•Urotherapy is a first-line treatment against enuresis In this review I will argue that much of what we do with these children is based more on experience and well-meant but poorly supported assumptions than on evidence. Some advice and therapies are probably ineffective whereas for other treatments we lack reliable predictors of treatment response. More research is obviously needed, but awaiting new results enuresis management could be substantially simplified.

The prevalence of urinary incontinence symptoms among multiparous women: a survey of Saudi health-care centers

OBJECTIVE

To determine the distribution of urinary incontinence (UI) symptoms and their relation to childbirth events.

METHODS

This cross-sectional study used a structured self-administered questionnaire that included the Questionnaire for Female Urinary Incontinence Diagnosis and the Urogenital Distress Inventory Short Form. The study included 802 women sampled from four primary health care centers in Dammam, KSA. A chi-square test and adjusted logistic regression models were used to examine the relation between UI symptoms and obstetric events.

RESULTS

Of the participants, 56.6% (n = 454) had at least one UI symptom. Symptoms were most commonly associated with grand multiparity (80.47%), a history of abortion (72%), assisted vaginal delivery (70%), an age of ≤ 18 years at first birth (66.67%) and ≥ 35 years at last birth (75.48%), and a history of macrosomia (84.62%) and episiotomy (67.89%). Unlike the risk of urgency UI, the risk of stress UI was statistically significantly linked to obstetric events. Grand multiparity was associated with a higher risk of both stress UI (odds ratio [OR]: 3.75, confidence interval [95% CI]: 1.68-8.40) and urgency UI (OR: 2.87, 95% CI: 1.07-7.73).

CONCLUSION

UI symptoms are common among grand multiparas. Unlike urgency UI, stress UI is associated with previous obstetric events.

Dysregulated NO/PDE5 signaling in the sickle cell mouse lower urinary tract: Reversal by oral nitrate therapy

AIMS

Nitric oxide (NO) has a critical, but not well understood, influence in the physiology of the lower urinary tract. We evaluated the effect of NO/phosphodiesterase (PDE)5 signaling in voiding dysfunction in the sickle cell disease (SCD) mouse, characterized by low NO bioavailability.

MAIN METHODS

Adult SCD (Sickle) and wild-type (WT) male mice were treated daily with sodium nitrate (10 mM) or vehicle. After 18 days, blood was obtained for nitrite measurement, urethra was collected for organ bath study, and bladder and urethra were collected for Western blot analysis of PDE5 phosphorylation (Ser-92) (activated form). Non-anesthetized mice underwent evaluation of urine volume by void spot assay. eNOS phosphorylation (Ser-1177) and nNOS phosphorylation (Ser-1412) (positive regulatory sites) were evaluated in the bladder and urethra of untreated mice.

KEY FINDINGS

Sickle mice exhibited decreased eNOS, nNOS, and PDE5 phosphorylation in the bladder and urethra, decreased plasma nitrite levels, increased relaxation of phenylephrine-contracted urethral tissue to an NO donor sodium nitroprusside, and increased total urine volume, compared with WT mice. Nitrate treatment normalized plasma nitrite levels, relaxation of urethra to sodium nitroprusside, PDE5 phosphorylation in the urethra and bladder, and urine volume in Sickle mice.

SIGNIFICANCE

Derangement in PDE5 activity associated with basally low NO bioavailability in the bladder and urethra contributes to the molecular basis for voiding abnormalities in Sickle mice. Inorganic nitrate supplementation normalized voiding in Sickle mice through mechanisms likely involving upregulation of PDE5 activity. These findings suggest that interventions targeting dysregulatory NO/PDE5 signaling may ameliorate overactive bladder in SCD.

Combination Pharmacotherapy for Treatment of Overactive Bladder (OAB)

Overactive bladder syndrome (OAB) negatively affects the quality of life of patients and their interactions with society. Treatment of OAB starts with behavioral modification and then pharmacotherapy using monotherapy with either antimuscarinics or β3 agonists. The third-line more invasive approaches are the next treatment option currently recommended. Both antimuscarinic agents and β3 agonists work through a different molecular pathway. This brings up the potential of having an additive effect when using a combination treatment for patients with OAB. Currently, the potential for using combination therapy to treat OAB in patients who had no improvement with a monotherapy approach before we attempt a more invasive approach is being explored. Several studies have shown the benefits of combination therapy which will be an additional option to the tools to treat OAB.

β3 -Adrenoceptors in the normal and diseased urinary bladder-What are the open questions?

β₃ -Adrenoceptor agonists are used in the treatment of overactive bladder syndrome. Although the relaxant response to adrenergic stimulation in human detrusor smooth muscle cells is mediated mainly via β₃ -adrenoceptors, the plasma concentrations of the therapeutic dose of mirabegron, the only clinically approved β₃ -adrenoceptor agonist, are considerably lower than the EC₅₀ for causing direct relaxation of human detrusor, suggesting a mechanism of action other than direct relaxation of detrusor smooth muscle. However, the site and mechanism of action of β₃ -adrenoceptor agonists in the bladder have not been firmly established. Postulated mechanisms include prejunctional suppression of ACh release from the parasympathetic nerves during the storage phase and inhibition of micro-contractions through β₃ -adrenoceptors on detrusor smooth muscle cells or suburothelial interstitial cells. Implications of possible desensitization of β₃ -adrenoceptors in the bladder upon prolonged agonist exposure and possible causes of rarely observed cardiovascular effects of mirabegron are also discussed. LINKED ARTICLES: This article is part of a themed section on Adrenoceptors-New Roles for Old Players. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.14/issuetoc.

The efficacy of mirabegron in the treatment of urgency and the potential utility of combination therapy

Urgency is the prevalent and most bothersome symptom of overactive bladder (OAB) and the treatment of urgency is the primary objective in the management of OAB. Urgency has a major impact on other symptoms of OAB and culminates in an increased frequency of micturition and reduced volume voided, which may contribute to shorter intervals between the need to void. Antimuscarinic agents and mirabegron, a β3-adrenoceptor agonist, constitute the main oral pharmacotherapeutic options for the treatment of urgency and other OAB symptoms. The reduction of urgency and other OAB symptoms significantly improve health-related quality of life. This review will explore the distinct mechanisms of action and effects of antimuscarinic agents and mirabegron, in relation to their effect on the pathophysiology of urgency. The review will also provide an overview of the various validated measurements of urgency and the numerous clinical trials regarding antimuscarinic agent monotherapy, mirabegron monotherapy, or combination treatment with mirabegron added on to the antimuscarinic agent solifenacin. A narrative review of the literature relating to pathophysiology of urgency, the validated measurements of urgency, and clinical trials relating to the pharmacological treatment of urgency. Antimuscarinic agent monotherapy, mirabegron monotherapy, or combination treatment with mirabegron added on to the antimuscarinic agent solifenacin statistically significantly reduce the symptoms of urgency compared with placebo. Combination therapy with mirabegron added on to solifenacin also statistically significantly reduces the symptoms of severe urgency compared with antimuscarinic agent monotherapy. A critique of the clinical benefits of combination therapy is also provided. Combination therapy provides an alternative treatment in patients with OAB that includes urgency who respond poorly to first-line monotherapy and who may otherwise often move on to more invasive treatments.

Basic and clinical aspects of antimuscarinic agents used to treat overactive bladder

Antimuscarinic agents are now widely used as the pharmacological therapy for overactive bladder (OAB) because neuronal (parasympathetic nerve) and non-neuronal acetylcholine play a significant role for the bladder function. In this review, we will highlight basic and clinical aspects of eight antimuscarinic agents (oxybutynin, propiverine, tolterodine, solifenacin, darifenacin, trospium, imidafenacin, and fesoterodine) clinically used to treat urinary dysfunction in patients with OAB. The basic pharmacological characteristics of these eight antimuscarinic agents include muscarinic receptor subtype selectivity, functional bladder selectivity, and muscarinic receptor binding in the bladder and other tissues. The measurement of drug-receptor binding after oral administration of these agents allows for clearer understanding of bladder selectivity by the integration of pharmacodynamics and pharmacokinetics under in vivo conditions. Their central nervous system (CNS) penetration potentials are also discussed in terms of the feasibility of impairments in memory and cognitive function in elderly patients with OAB. The clinical aspects of efficacy focus on improvements in the daytime urinary frequency, nocturia, bladder capacity, the frequency of urgency, severity of urgency, number of incontinence episodes, OAB symptom score, and quality of life (QOL) score by antimuscarinic agents in patients with OAB. The safety of and adverse events caused by treatments with antimuscarinic agents such as dry mouth, constipation, blurred vision, erythema, fatigue, increased sweating, urinary retention, and CNS adverse events are discussed. A dose-dependent relationship was observed with adverse events, because the risk ratio generally increased with elevations in the drug dose of antimuscarinic agents. Side effect profiles may be additive to or contraindicated by other medications.

What are the origins and relevance of spontaneous bladder contractions? ICI-RS 2017

INTRODUCTION

Storage phase bladder activity is a counter-intuitive observation of spontaneous contractions. They are potentially an intrinsic feature of the smooth muscle, but interstitial cells in the mucosa and the detrusor itself, as well as other muscular elements in the mucosa may substantially influence them. They are identified in several models explaining lower urinary tract dysfunction.

METHODS

A consensus meeting at the International Consultation on Incontinence Research Society (ICI-RS) 2017 congress considered the origins and relevance of spontaneous bladder contractions by debating which cell type(s) modulate bladder spontaneous activity, whether the methodologies are sufficiently robust, and implications for healthy and abnormal lower urinary tract function.

RESULTS

The identified research priorities reflect a wide range of unknown aspects. Cellular contributions to spontaneous contractions in detrusor smooth muscle are still uncertain. Accordingly, insight into the cellular physiology of the bladder wall, particularly smooth muscle cells, interstitial cells, and urothelium, remains important. Upstream influences, such as innervation, endocrine, and paracrine factors, are particularly important. The cellular interactions represent the key understanding to derive the integrative physiology of organ function, notably the nature of signalling between mucosa and detrusor layers. Indeed, it is still not clear to what extent spontaneous contractions generated in isolated preparations mirror their normal and pathological counterparts in the intact bladder. Improved models of how spontaneous contractions influence pressure generation and sensory nerve function are also needed.

CONCLUSIONS

Deriving approaches to robust evaluation of spontaneous contractions and their influences for experimental and clinical use could yield considerable progress in functional urology.

Overactive bladder in children

Overactive bladder (OAB) is a ubiquitous syndrome that is defined by urinary urgency with, or without urinary incontinence. OAB is observed in all parts of the world, with a prevalence of 5-12% in children (5-10 years of age) and a prevalence of 0.5% in older adolescents (16-18 years of age). Published data indicate that around a third of children with OAB are likely to become adults with similar complaints. Studies in children and in adults with OAB indicate that these individuals are more likely to also have anxiety, depression and attention deficit problems, and that appropriate treatment of these comorbidities can often improve the patient's OAB symptoms. Furthermore, data from twin studies and familial surveys seem to indicate a genetic component of OAB. Pharmacological treatments of OAB in children have improved in the past 5 years, moving beyond anticholinergic agents and including the off-label use of α-blockers, β3-agonists and intravesical botulinum toxin. Use of several different electrical stimulation techniques is also effective, both as first-line treatments, and for patients with treatment-refractory symptoms. Overall the outlook of children with OAB seems to be improving, with a greater understanding of the pathophysiology of this syndrome. Treatment modalities that target the source of the underlying problem, especially in children, are likely to provide the best patient outcomes.

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.

Chapter 2: Pathophysiology of neurogenic detrusor overactivity and the symptom complex of "overactive bladder"

It is now clearly recognized that the function of the lower urinary tract represents a complex interaction between the bladder and its outlet, acting under the control of the central nervous system. While in the past attention has principally focused on the motor (efferent) control of the bladder, sensory (afferent) innervation is now known to be an important therapeutic target. This change in emphasis is strongly supported by both basic science and clinical evidence demonstrating the efficacy of therapy directed at the afferent system. This chapter summarizes the neurophysiological control mechanism that underpins normal lower urinary tract function, emphasizing the importance of the afferent system as a potential therapeutic target.

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.

Defining response and non-response to treatment in patients with overactive bladder: a systematic review

OBJECTIVE

There is currently a lack of formal guidance for assessing treatment response and non-response in patients with overactive bladder (OAB). Such guidance would be useful for both clinical practice and the design of clinical trials. Our purpose was to review and assess definitions of treatment response and non-response used in patients with OAB.

METHODS

We conducted a systematic review of articles published between January 1, 2005 and August 8, 2013 using PubMed. Search terms included (overactive bladder) AND ('treatment response' OR responder OR success OR satisfied OR goal OR refractory OR nonresponder OR fail OR persistent OR dissatisfied). Limits were 'humans' and 'English'. Studies conducted in subjects with neurogenic detrusor overactivity, conditions other than OAB, or OAB symptoms following lower urinary tract/pelvic surgery were excluded; case reports and letters were also excluded.

RESULTS

The literature search returned 423 articles, of which 75 met the inclusion criteria and defined a specific threshold by which treatment response or non-response was determined for patients receiving behavioral therapy and/or treatment with an antimuscarinic, β3-agonist, botulinum toxin, or neural stimulation. One published abstract from congress proceedings and three additional articles that were not identified by the search were included; thus, a total of 79 records were included. A wide variety of symptom-based definitions and patient-reported outcomes (PROs) were used. Symptom-based definitions frequently used a threshold of 50-100% improvement in general or specific symptoms; urgency urinary incontinence (UUI) was often used in studies with incontinent patients. Definitions based on PROs frequently used measures of satisfaction, general improvement, or goal achievement. Studies of patients with refractory OAB often referred to a failure to respond to ≥1 other therapy, or to poor efficacy or unacceptable tolerability, without further specification. Limitations of this review are that only English language articles were included and that only the PubMed database was used for the literature search.

CONCLUSIONS

There is considerable heterogeneity in the definitions of treatment response and non-response in trials of patients with OAB; some standardization would be beneficial. However, there is also heterogeneity among patients of what constitutes treatment success or failure, and conceptualizations of treatment response and non-response in both clinical trials and clinical practice must take patient characteristics into account. For patients with UUI, it is recommended that the criteria for treatment response include this symptom, as measured by change in the absolute number of UUI episodes or achievement of continence, given its impact on patients' lives and associated bother. PROs provide important information that confirm symptom-based measures by demonstrating that observed changes in symptoms are meaningful to the patient. In clinical practice, measures of treatment satisfaction and goal achievement can be highly useful.

Urgency and pain in patients with overactive bladder and bladder pain syndrome. What are the differences?

BACKGROUND

The Overactive Bladder Syndrome (OAB) and the Bladder Pain Syndrome/Interstitial Cystitis (BPS/IC) are different urological conditions sharing 'urgency' as a common symptom. The aim of this review is to address our existing knowledge and establish how these symptoms are interrelated and to determine whether or not there is a common link between both symptoms complexes that help to distinguish one from the other.

METHODS

Pubmed was used to obtain references for this non-systematic review aiming to discuss differences between OAB and BPS/IC. Guidelines of several professional associations and discussions based on expert opinion from the authors were implemented.

RESULTS

Whilst in BPS the hallmark symptom is pain on bladder filling, urgency is the defining symptom of OAB. Whilst it is likely that the pain in BPS/IC arises from local inflammation in the bladder wall, the nature of urgency as a symptom, its origin, and the relationship between urgency and pain, as well as the different afferent mechanisms associated with the genesis of these sensory symptoms, remains unknown. Although the aetiology of both OAB and PBS/IC is unclear, the influence of environmental factors has been suggested. Both are chronic conditions with very variable symptom resolution and response to therapy. The relationship with voiding dysfunction, gynaecological causes of chronic pelvic pain or the possible alteration of the hypothalamic-pituitary-adrenal axis and psychological disorders has not been established. Inflammation has been suggested as the common link between OAB and BPS/IC.

CONCLUSIONS

OAB and BPS/IC are different symptoms complexes that share urgency as a common symptom. None of them have a specific symptom although pain on bladder filling is the hallmark symptom in BPS/IC. Bladder pain with urgency should be a trigger for referral to the provider with appropriate knowledge and expertise in this disease state, whereas the management of OAB should be part of normal routine care in the community.

Descriptors of sensation confirm the multidimensional nature of desire to void

AIMS

To collect and categorize descriptors of "desire to void" sensation, determine the reliability of descriptor categories and assess whether descriptor categories discriminate between people with and without symptoms of overactive bladder.

METHODS

This observational, repeated measures study involved 64 Australian volunteers (47 female), aged 50 years or more, with and without symptoms of overactive bladder. Descriptors of desire to void sensation were derived from a structured interview (conducted on two occasions, 1 week apart). Descriptors were recorded verbatim and categorized in a three-stage process. Overactive bladder status was determined by the Overactive Bladder Awareness Tool and the Overactive Bladder Symptom Score. McNemar's test assessed the reliability of descriptors volunteered between two occasions and Partial Least Squares Regression determined whether language categories discriminated according to overactive bladder status. Post hoc Chi squared analysis and relative risk calculation determined the size and direction of overactive bladder prediction.

RESULTS

Thirteen language categories (Urgency, Fullness, Pressure, Tickle/tingle, Pain/ache, Heavy, Normal, Intense, Sudden, Annoying, Uncomfortable, Anxiety, and Unique somatic) encapsulated 344 descriptors of sensation. Descriptor categories were stable between two interviews. The categories "Urgency" and "Fullness" predicted overactive bladder status. Participants who volunteered "Urgency" descriptors were twice as likely to have overactive bladder and participants who volunteered "Fullness" descriptors were almost three times as likely not to have overactive bladder.

CONCLUSIONS

The sensation of desire to void is reliably described over sessions separated by a week, the language used reflects multiple dimensions of sensation, and can predict overactive bladder status.

OnabotulinumtoxinA significantly attenuates bladder afferent nerve firing and inhibits ATP release from the urothelium

OBJECTIVE

To investigate the direct effect of onabotulinumtoxinA (OnaBotA) on bladder afferent nerve activity and release of ATP and acetylcholine (ACh) from the urothelium.

MATERIALS AND METHODS

Bladder afferent nerve activity was recorded using an in vitro mouse preparation enabling simultaneous recordings of afferent nerve firing and intravesical pressure during bladder distension. Intraluminal and extraluminal ATP, ACh, and nitric oxide (NO) release were measured using the luciferin-luciferase and Amplex(®) Red assays (Molecular Probes, Carlsbad, CA, USA), and fluorometric assay kit, respectively. OnaBotA (2U), was applied intraluminally, during bladder distension, and its effect was monitored for 2 h after application. Whole-nerve activity was analysed to classify the single afferent units responding to physiological (low-threshold [LT] afferent <15 mmHg) and supra-physiological (high-threshold [HT] afferent >15 mmHg) distension pressures.

RESULTS

Bladder distension evoked reproducible pressure-dependent increases in afferent nerve firing. After exposure to OnaBotA, both LT and HT afferent units were significantly attenuated. OnaBotA also significantly inhibited ATP release from the urothelium and increased NO release.

CONCLUSION

These data indicate that OnaBotA attenuates the bladder afferent nerves involved in micturition and bladder sensation, suggesting that OnaBotA may exert its clinical effects on urinary urgency and the other symptoms of overactive bladder syndrome through its marked effect on afferent nerves.

Mirabegron for the treatment of overactive bladder: a prespecified pooled efficacy analysis and pooled safety analysis of three randomised, double-blind, placebo-controlled, phase III studies

INTRODUCTION

To examine pooled efficacy data from three, large phase III studies comparing mirabegron (50 and 100 mg) with placebo, and pooled safety data including additional mirabegron 25 mg and tolterodine extended release (ER) 4 mg results.

METHODS

This prespecified pooled analysis of three randomised, double-blind, placebo-controlled, 12-week studies, evaluated efficacy and safety of once-daily mirabegron 25 mg (safety analysis), 50 or 100 mg (efficacy and safety analyses) and tolterodine ER 4 mg (safety analysis) for the treatment of symptoms of overactive bladder (OAB). Co-primary efficacy measures were change from baseline to Final Visit in the mean number of incontinence episodes/24 h and mean number of micturitions/24 h. Key secondary efficacy end-points included mean number of urgency episodes/24 h and mean volume voided/micturitions, while other end-points included patient-reported outcomes according to the Treatment Satisfaction-Visual Analogue Scale (TS-VAS) and responder analyses [dry rate (posttreatment), ≥ 50% reduction in incontinence episodes/24 h, ≤ 8 micturitions/24 h (post hoc analysis)]. The safety analysis included adverse event (AE) reporting, laboratory assessments, ECG, postvoid residual volume and vital signs (blood pressure, pulse rate).

RESULTS

Mirabegron (50 and 100 mg once daily) demonstrated statistically significant improvements compared with placebo for the co-primary end-points, key secondary efficacy variables, TS-VAS and responder analyses (all comparisons p < 0.05). Mirabegron is well tolerated and demonstrates a good safety profile. The most common AEs (≥ 3%) included hypertension, nasopharyngitis and urinary tract infection (UTI); the incidence of hypertensive events and UTIs decreased with increasing dose. For mirabegron, the incidence of the bothersome antimuscarinic AE, dry mouth, was at placebo level and of a lesser magnitude than tolterodine.

CONCLUSION

The efficacy and safety of mirabegron are demonstrated in this large pooled clinical trial dataset in patients with OAB.

A proof-of-concept study: mirabegron, a new therapy for overactive bladder

AIMS

To evaluate the potential of mirabegron, a selective β3-adrenoceptor agonist, for treatment of overactive bladder (OAB) symptoms.

METHODS

A multicenter, randomized, double-blind, double-dummy, parallel group, placebo and active-controlled, Phase 2, proof-of-concept study was conducted. Eligible patients (n = 314) were enrolled into a single-blind, 2-week placebo run-in period followed by a randomized, double-blind, placebo-controlled treatment period. Patients received mirabegron 100 or 150 mg twice-daily (BID), placebo or tolterodine 4 mg extended release (ER) once-daily for 4 weeks. Primary endpoint was change from baseline to end-of-treatment in mean number of micturition episodes per 24 hr. Secondary endpoints included changes in mean volume voided per micturition; mean number of urinary incontinence, urgency urinary incontinence, and urgency episodes per 24 hr; severity of urgency; nocturia, and quality of life measures. Safety parameters included adverse events, laboratory tests, electrocardiogram parameters and post-void residual volume.

RESULTS

Mirabegron 100 and 150 mg BID resulted in a statistically significant improvement versus placebo in mean change from baseline to end-of-treatment in the primary endpoint of micturition frequency (2.2 micturitions/24 hr vs. 1.2 micturitions/24 hr for both doses, adjusted P ≤ 0.01 for both comparisons). Mirabegron had a statistically significant effect versus placebo for most secondary endpoints, including quality of life variables. Despite a small increase in pulse rate, mirabegron demonstrated good safety and tolerability.

CONCLUSIONS

Mirabegron was efficacious and well tolerated in patients with OAB symptoms and heralds the first of a new class of oral pharmacological therapy for OAB for more than 30 years.

Autonomic nervous control of the urinary bladder

The autonomic nervous system plays an important role in the regulation of the urinary bladder function. Under physiological circumstances, noradrenaline, acting mainly on β(3) -adrenoceptors in the detrusor and on α(1) (A) -adrenoceptors in the bladder outflow tract, promotes urine storage, whereas neuronally released acetylcholine acting mainly on M(3) receptors promotes bladder emptying. Under pathophysiological conditions, however, this system may change in several ways. Firstly, there may be plasticity at the levels of innervation and receptor expression and function. Secondly, non-neuronal acetylcholine synthesis and release from the urothelium may occur during the storage phase, leading to a concomitant exposure of detrusor smooth muscle, urothelium and afferent nerves to acetylcholine and noradrenaline. This can cause interactions between the adrenergic and cholinergic system, which have been studied mostly at the post-junctional smooth muscle level until now. The implications of such plasticity are being discussed.

Nocturia: current concepts and future perspectives

Nocturia is a prevalent highly bothersome urinary symptom that may significantly detriment the health and well-being of sufferers. It is characterized by waking at night to void, each void preceded and followed by sleep, hence leading to fragmentation of sleep and day-time tiredness. This may result in reduced productivity in the workplace, which contributes to the significant burden to the wider society that nocturia incurs. Nocturia was traditionally viewed as one of the many urinary tract symptoms that occur due to lower urinary tract dysfunction. However, recently it has been recognized that due to its multi-factorial aetio-pathogenesis, nocturia should be viewed as distinct clinical condition in its own right. Careful assessment of the nocturic patient is essential so that treatment strategies are guided by the likely causes. Much research is currently being undertaken into the underlying causes and the optimal management approaches. This review will explore the contemporary status of research on nocturia with a focus on the current and newly available pharmacotherapies.

Brain activity underlying impaired continence control in older women with overactive bladder

AIMS

To identify, in subjects with overactive bladder (OAB), differences in brain activity between those who maintained and those who lost bladder control during functional magnetic resonance imaging (fMRI) of the brain with simultaneous urodynamics.

METHODS

Secondary analysis of a cohort of older women (aged >60) with proven urgency urinary incontinence, who, in the scanner, either developed detrusor overactivity and incontinence (the "DO group") or did not (the "no DO" group). A priori hypothesis: during urgency provoked by bladder filling, without DO, activity in regions related to continence control is diminished in the DO group; specifically (1a) less activation in supplementary motor area (SMA) and (1b) less deactivation in prefrontal cortex (PFC) and parahippocampal complex (PH). We also explored phenotypic (clinical and urodynamic) differences between the groups.

RESULTS

During urgency preceding DO, the DO group showed stronger activation in SMA and adjacent regions (hypothesis 1a rejected), and less deactivation in PH but no significant difference in PFC (hypothesis 1b partially accepted). These subjects were older, with more changes in brain's white matter, decreased tolerance of bladder filling and greater burden of incontinence.

CONCLUSIONS

(1) In older women with OAB, brain activity in the SMA is greater among those with more easily elicitable DO, suggesting a compensatory response to failure of control elsewhere. (2) OAB is heterogeneous; one possible phenotype shows severe functional impairment attributable partly to age-related white matter changes. (3) Functional brain imaging coupled with urodynamics may provide CNS markers of impaired continence control in subjects with OAB.

A comprehensive non-clinical evaluation of the CNS penetration potential of antimuscarinic agents for the treatment of overactive bladder

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

This study provides antimuscarinic agents for overactive bladder (OAB) display variable association with side effects mediated by the central nervous system (CNS), which may be of particular concern in the elderly. Adverse effects on CNS functioning are related to muscarinic receptor subtype selectivity and the ability of the agent to cross the blood-brain barrier, where P-gp plays a role in limiting permeability.

WHAT THIS STUDY ADDS

This study provides a parallel investigation of CNS penetration of antimuscarinic OAB agents in vivo and assessment of physical properties and permeability in cell monolayers in vitro. It adds further understanding of the roles of passive transcellular permeability and P-gp in determining CNS penetration of antimuscarinic OAB agents. It also enables a comparison of CNS side-effect profiles of OAB agents with preclinical CNS penetration data.

AIMS

To assess and compare the mechanisms of central nervous system (CNS) penetration of antimuscarinic overactive bladder (OAB) agents.

METHODS

Physical properties were computed or compiled from the literature. Rats were administered 5-hydroxymethyl tolterodine (HMT), darifenacin, oxybutynin, solifenacin, tolterodine or trospium subcutaneously. At 1 h postdose, plasma, brain and cerebrospinal fluid (CSF) concentrations were determined using LC-MS/MS assays. Brain and plasma protein binding were determined in vitro. Permeability in the presence and absence of the efflux transporter P-glycoprotein (P-gp) was assessed in RRCK and MDCK-MDR1 transwell assays.

RESULTS

Oxybutynin displayed extensive CNS penetration, with brain:plasma ratios (B:P), unbound brain:unbound plasma ratios (Kp,free) and CSF:free plasma ratios each >1. Tolterodine (B:P = 2.95, Kp,free = 0.23 and CSF:free plasma = 0.16) and solifenacin (B:P = 3.04, Kp,free = 0.28 and CSF:free plasma = 1.41) showed significant CNS penetration but with some restriction from CNS as indicated by Kp,free values significantly <1. 5-HMT, darifenacin and trospium displayed much lower B:P (0.03-0.16), Kp,free (0.01-0.04) and CSF:free plasma (0.004-0.06), consistent with poor CNS penetration. Permeability in RRCK cells was low for trospium (0.63 × 10(-6) cm s(-1) ), moderate for 5-HMT (11.7 × 10(-6) cm s(-1) ) and high for darifenacin, solifenacin, tolterodine and oxybutynin (21.5-38.2 × 10(-6) cm s(-1) ). In MDCK-MDR1 cells 5-HMT, darifenacin and trospium, were P-gp substrates, whereas oxybutynin, solifenacin and tolterodine were not P-gp substrates.

CONCLUSIONS

Brain penetration was low for antimuscarinics that are P-gp substrates (5-HMT, darifenacin and trospium), and significant for those that are not P-gp substrates (oxybutynin, solifenacin and tolterodine). CNS adverse events reported in randomized controlled clinical trials show general alignment with the preclinical data described in this study.

Pathophysiology of the urothelium and detrusor

Conventional wisdom now agrees that symptoms of overactive bladder (OAB) seem to emanate from an aberration in the voiding reflex, leading to involuntary detrusor contractions of either neurogenic or myogenic origin. Furthermore, emerging evidence also encourages us to adopt a new paradigm, in which bladder urothelium is not just a simple barrier but an active contributor to bladder function. In this paradigm, aberration in sensory mechanisms emanating from the urothelium can also contribute to OAB symptoms through altered excitability of afferents in the bladder leading to increased bladder sensation. The high density of muscarinic receptors expressed on urothelium can not only mediate release of urothelium-derived inhibitory factor, but can also be seen as an alternative site of action for antimuscarinic drugs. Urothelium also expresses a host of other receptors such as TRPV1 and TRPM8, whose functional role is yet to be confirmed.

Role of KIT-Positive Interstitial Cells of Cajal in the Urinary Bladder and Possible Therapeutic Target for Overactive Bladder

In the gastrointestinal tract, interstitial cells of Cajal (ICCs) act as pacemaker cells to generate slow wave activity. Interstitial cells that resemble ICCs in the gastrointestinal tract have been identified by their morphological characteristics in the bladder. KIT is used as an identification marker of ICCs. ICCs in the bladder may be involved in signal transmission between smooth muscle bundles, from efferent nerves to smooth muscles, and from the urothelium to afferent nerves. Recent research has suggested that not only the disturbance of spontaneous contractility caused by altered detrusor ICC signal transduction between nerves and smooth muscle cells but also the disturbance of signal transduction between urothelial cells and sensory nerves via suburothelial ICC may induce overactive bladder (OAB). Recent reports have suggested that KIT is not only a detection marker of these cells, but also may play a crucial role in the control of bladder function. Research into the effect of a c-kit receptor inhibitor, imatinib mesylate, on bladder function implies that KIT-positive ICCs may be therapeutic target cells to reduce bladder overactivity and that the blockage of c-kit receptor may offer a new therapeutic strategy for OAB treatment, although further study will be needed.

β-adrenoceptor agonist effects in experimental models of bladder dysfunction

β-adrenoceptor stimulation can enhance the storage function of the urinary bladder by acting on detrusor smooth muscle tone, mediator release from the urothelium and/or afferent nerve activity. In humans this may occur predominantly if not exclusively via the β₃-subtype. The effects of β-adrenoceptor agonists including several β₃-selective agonists have been studied in vitro and in vivo, in healthy animals of both genders and various age groups and in a wide range of animal (mostly rat) models of genetic or acquired bladder dysfunction. Such models included bladder irritation by intravesical instillation of acetic acid or prostaglandin E₂, bladder outlet obstruction, stroke, diabetes, spontaneously hypertensive rats, and NO synthase inhibition. Across all of these models β-adrenoceptor agonists had effects consistent with improved bladder storage function. β₃-adrenoceptor effects are resistant to agonist-induced desensitization in many cell types, but whether this also applies to the human bladder is unknown. The efficacy of β-adrenoceptor agonists appears to be largely unaffected by common polymorphisms of the β₃-adrenoceptor gene. Taken together these findings suggest that β₃-adrenoceptor agonists may become useful drugs for the treatment of bladder storage dysfunction, a view supported by recent phase III clinical studies for one such agent, mirabegron.

Bladder symptoms in multiple sclerosis: a review of pathophysiology and management

IMPORTANCE OF THE FIELD

The use of anticholinergic medication in bladder dysfunction such as overactive bladder syndrome (OAB) is widespread. However, the benefits and risks of anticholinergics in multiple sclerosis (MS) are unclear because in MS the damage to normal urinary function is both more diffuse and increases with disease progression, and the risk of CNS side effects is higher.

AREAS COVERED IN THIS REVIEW

The pathophysiology of urinary dysfunction in MS and the efficacy and side effects of anticholinergics is assessed. The review analyzed randomized controlled trials and observational studies using anticholinergics involving persons with a confirmed diagnosis of MS having urinary symptoms. Finally a pragmatic approach to managing urinary symptoms in MS is discussed.

WHAT THE READER WILL GAIN

The published data provide limited evidence for the efficacy of anticholinergics in MS. The complexity of treating urinary symptoms in the context of other therapies and the changing neurological background seen in MS is comprehensively analyzed.

TAKE HOME MESSAGE

Anticholinergics could be helpful in particular phases of MS. However, there is inadequate evidence currently available on the use of anticholinergics in MS, and further research on the management of the MS neuropathic bladder is warranted.

β-Adrenergic Receptor Subtypes in the Urinary Tract

Within the urinary tract, β-adrenergic receptors (AR) are found largely on smooth muscle cells but are also present, at least in the bladder, in the urothelium and on afferent nerves. Our understanding of β-AR subtype expression and function is hampered by a lack of well-validated tools, particularly with regard to β(3)-AR. Moreover, the β-AR subtypes involved in a specific function may differ between species. In the ureter, β-AR can modulate pacemaker activity and smooth muscle tone involving multiple subtypes. In the human bladder, β-AR promote urine storage. Bladder smooth muscle relaxation primarily involves β(3)-AR, and the agonists selective for this subtype are in clinical development to treat bladder dysfunction. While prostate and urethra also express β-AR, the overall physiological role in these tissues remains unclear.

Overview on the lower urinary tract

This chapter overviews our current knowledge on the subject of the urinary tract, whose fundamental role is to transport urine from the kidneys and then store it at low pressure in the lower urinary tract until it can be voided at a socially convenient time. Current understanding of lower urinary tract function and dysfunction is summarized, with reference to anatomy, innervation, and function. The importance of the neurological system in the normal function of the lower urinary tract is emphasized, with a brief overview of the consequence of neural injury at different levels within the central nervous system. The role of urodynamics in the evaluation of lower urinary tract symptoms is discussed with particular reference to the currently recommended terminology advocated by the International Continence Society and The International Urogynaecological Association.

Do gender, age or lifestyle factors affect responses to antimuscarinic treatment in overactive bladder patients?

AIMS

Gender, age, obesity, smoking and alcohol or caffeine intake have been shown or proposed to be risk factors for the prevalence and/or severity of the overactive bladder symptom complex (OAB) or related parameters. We have explored whether any of these factors affect the therapeutic response to a muscarinic receptor antagonist during routine clinical use.

METHODS

Data were analysed from 3766 OAB patients (77.1% woman, age 62.6 +/- 12.8 years) participating in an observational, open-label postmarketing surveillance study of the safety and efficacy of darifenacin. Multiple logistic regression models were applied to explore the effect of potential OAB risk factors on the darifenacin treatment-associated improvement of OAB symptoms, patient's subjective rating of bladder problems and global efficacy and tolerability.

RESULTS

Age and (less consistently) gender were statistically significantly correlated with efficacy parameters, but the extent of their impact was judged to be too small to be clinically relevant. Except for a very small effect of body mass index on urgency episode improvement, none of the lifestyle-associated factors had significant effects on the efficacy of darifenacin. Except for a very small age effect, none of the potential risk factors had significant effects on global tolerability.

DISCUSSION AND CONCLUSIONS

We conclude that the efficacy and tolerability of a muscarinic receptor antagonist, such as darifenacin is largely independent of potential OAB risk factors, such as gender, age, obesity, smoking and alcohol or caffeine intake.

Overactive bladder is not only overactive but also hypersensitive

OBJECTIVES

To evaluate differences in bladder filling sensations and current perception threshold (CPT) values between patients with and without overactive bladder (OAB), and to further investigate the correlation between CPT values and voiding patterns in OAB patients.

METHODS

Detrusor overactivity and bladder volumes at first sensation of bladder filling, first desire to void, and strong desire to void during filling cystometry were compared between 55 female patients with OAB and 42 with non-OAB. CPT measurements from the bladder mucosa taken after neuroselective electrostimulation at frequencies of 2000, 250, and 5 Hz were compared between the 2 groups. In OAB patients, the correlations between CPT values and voiding variables based on 3-day bladder diaries were investigated.

RESULTS

OAB patients showed significantly more detrusor overactivity than non-OAB patients (P <.05). Bladder volumes at first sensation of bladder filling, first desire to void, and strong desire to void were significantly lower in OAB patients than in non-OAB patients (P <.05). CPT values at all 3 frequencies were also significantly lower in OAB patients (P <.05). The total number of urgency episodes correlated with CPT values at 250 (r = -0.274, P = .045) and 5 Hz (r = -0.293, P = .032). The total number of urge incontinence episodes also correlated with CPT values at 250 (r = -0.279, P = .041) and 5 Hz (r = -0.272, P = .046).

CONCLUSIONS

Bladder sensory profiles displayed a more sensitive bladder in OAB patients compared with non-OAB subjects. OAB patients may have bladders that are not only overactive, but also hypersensitive.