THE ROLE OF BLADDER AFFERENT PATHWAYS IN BLADDER HYPERACTIVITY INDUCED BY THE INTRAVESICAL ADMINISTRATION OF NERVE GROWTH FACTOR

Pathophysiology of Overactive Bladder and Pharmacologic Treatments Including β3-Adrenoceptor Agonists -Basic Research Perspectives

Overactive bladder (OAB) is a symptom-based syndrome defined by urinary urgency, frequency, and nocturia with or without urge incontinence. The causative pathology is diverse; including bladder outlet obstruction (BOO), bladder ischemia, aging, metabolic syndrome, psychological stress, affective disorder, urinary microbiome, localized and systemic inflammatory responses, etc. Several hypotheses have been suggested as mechanisms of OAB generation; among them, neurogenic, myogenic, and urothelial mechanisms are well-known hypotheses. Also, a series of local signals called autonomous myogenic contraction, micromotion, or afferent noises, which can occur during bladder filling, may be induced by the leak of acetylcholine (ACh) or urothelial release of adenosine triphosphate (ATP). They can be transmitted to the central nervous system through afferent fibers to trigger coordinated urgency-related detrusor contractions. Antimuscarinics, commonly known to induce smooth muscle relaxation by competitive blockage of muscarinic receptors in the parasympathetic postganglionic nerve, have a minimal effect on detrusor contraction within therapeutic doses. In fact, they have a predominant role in preventing signals in the afferent nerve transmission process. β3-adrenergic receptor (AR) agonists inhibit afferent signals by predominant inhibition of mechanosensitive Aδ-fibers in the normal bladder. However, in pathologic conditions such as spinal cord injury, it seems to inhibit capsaicin-sensitive C-fibers. Particularly, mirabegron, a β3-agonist, prevents ACh release in the BOO-induced detrusor overactivity model by parasympathetic prejunctional mechanisms. A recent study also revealed that vibegron may have 2 mechanisms of action: inhibition of ACh from cholinergic efferent nerves in the detrusor and afferent inhibition via urothelial β3-AR.

Molecular Mechanisms of Neurogenic Lower Urinary Tract Dysfunction after Spinal Cord Injury

This article provides a synopsis of current progress made in fundamental studies of lower urinary tract dysfunction (LUTD) after spinal cord injury (SCI) above the sacral level. Animal models of SCI allowed us to examine the effects of SCI on the micturition control and the underlying neurophysiological processes of SCI-induced LUTD. Urine storage and elimination are the two primary functions of the LUT, which are governed by complicated regulatory mechanisms in the central and peripheral nervous systems. These neural systems control the action of two functional units in the LUT: the urinary bladder and an outlet consisting of the bladder neck, urethral sphincters, and pelvic-floor striated muscles. During the storage phase, the outlet is closed, and the bladder is inactive to maintain a low intravenous pressure and continence. In contrast, during the voiding phase, the outlet relaxes, and the bladder contracts to facilitate adequate urine flow and bladder emptying. SCI disrupts the normal reflex circuits that regulate co-ordinated bladder and urethral sphincter function, leading to involuntary and inefficient voiding. Following SCI, a spinal micturition reflex pathway develops to induce an overactive bladder condition following the initial areflexic phase. In addition, without proper bladder-urethral-sphincter coordination after SCI, the bladder is not emptied as effectively as in the normal condition. Previous studies using animal models of SCI have shown that hyperexcitability of C-fiber bladder afferent pathways is a fundamental pathophysiological mechanism, inducing neurogenic LUTD, especially detrusor overactivity during the storage phase. SCI also induces neurogenic LUTD during the voiding phase, known as detrusor sphincter dyssynergia, likely due to hyperexcitability of Aδ-fiber bladder afferent pathways rather than C-fiber afferents. The molecular mechanisms underlying SCI-induced LUTD are multifactorial; previous studies have identified significant changes in the expression of various molecules in the peripheral organs and afferent nerves projecting to the spinal cord, including growth factors, ion channels, receptors and neurotransmitters. These findings in animal models of SCI and neurogenic LUTD should increase our understanding of pathophysiological mechanisms of LUTD after SCI for the future development of novel therapies for SCI patients with LUTD.

Stress-induced symptom exacerbation: Stress increases voiding frequency, somatic sensitivity, and urinary bladder NGF and BDNF expression in mice with subthreshold cyclophosphamide (CYP)

Symptom exacerbation due to stress is prevalent in many disease states, including functional disorders of the urinary bladder (e.g., overactive bladder (OAB), interstitial cystitis/bladder pain syndrome (IC/BPS)); however, the mechanisms underlying the effects of stress on micturition reflex function are unclear. In this study we designed and evaluated a stress-induced symptom exacerbation (SISE) mouse model that demonstrates increased urinary frequency and somatic (pelvic and hindpaw) sensitivity. Cyclophosphamide (CYP) (35 mg/kg; i.p., every 48 hours for a total of 4 doses) or 7 days of repeated variate stress (RVS) did not alter urinary bladder function or somatic sensitivity; however, both CYP alone and RVS alone significantly (p ≤ 0.01) decreased weight gain and increased serum corticosterone. CYP treatment when combined with RVS for 7 days (CYP+RVS) significantly (p ≤ 0.01) increased serum corticosterone, urinary frequency and somatic sensitivity and decreased weight gain. CYP+RVS exposure in mice significantly (p ≤ 0.01) increased (2.6-fold) voiding frequency as we determined using conscious, open-outlet cystometry. CYP+RVS significantly (p ≤ 0.05) increased baseline, threshold, and peak micturition pressures. We also evaluated the expression of NGF, BDNF, CXC chemokines and IL-6 in urinary bladder in CYP alone, RVS alone and CYP+RVS mouse cohorts. Although all treatments or exposures increased urinary bladder NGF, BDNF, CXC and IL-6 content, CYP+RVS produced the largest increase in all inflammatory mediators examined. These results demonstrated that CYP alone or RVS alone creates a change in the inflammatory environment of the urinary bladder but does not result in a change in bladder function or somatic sensitivity until CYP is combined with RVS (CYP+RVS). The SISE model of CYP+RVS will be useful to develop testable hypotheses addressing underlying mechanisms where psychological stress exacerbates symptoms in functional bladder disorders leading to identification of targets and potential treatments.

Current Understanding of the Pathophysiology and Novel Treatments of Interstitial Cystitis/Bladder Pain Syndrome

The pathophysiology of interstitial cystitis/bladder pain syndrome (IC/BPS) is multifactorial. Identifying the clinical characteristics and cystoscopic findings of bladder-centered IC/BPS facilitates optimal treatment strategies targeting the diseased urinary bladder. Patients with Hunner’s lesion (HIC) and without Hunner’s lesion (NHIC) should be treated differently. Based on the histopathological findings, NHIC can be treated with intravesical instillation of urothelial protective agents, such as hyaluronic acid, to cover the urothelial defects. In non-responders, chronic inflammation and higher urothelial dysfunction can be treated with intravesical botulinum toxin A injection, platelet-rich plasma injection, or low-energy shock wave treatment to reduce inflammation, increase tissue regeneration, and improve the urothelial barrier. Patients with HIC should be treated with electrocauterization first; augmentation enterocystoplasty should only be used in end-stage HIC when the contracted bladder is refractory to other treatments. The antiviral agent, valacyclovir, can be used in patients with HIC, small bladder capacity, and high-grade glomerulations. In addition, behavioral modification is always recommended from the beginning of treatment. Treatment with cognitive behavioral therapy interventions in combination with bladder therapy can reduce anxiety and improve treatment outcomes. Herein, recent advances in the pathophysiology and novel treatments for IC/BPS are reviewed.

Cystitis Induces Altered CREB Expression Related with Micturition Reflex

Background and objectives: Bladder stimulation upregulates neurotrophins associated with voiding reflex. Bacterial cystitis can be a stimulant that activates this system, resulting in a pathological state. Phosphorylated responsive element of binding protein (p-CREB) is a pivotal transcriptional factor in the neurotrophin signaling cascade. The goal of our study was to examine the change in expression of p-CREB in dorsal root ganglia (DRG) of rats after uropathogenic Escherichia coli infection of the bladder. Materials and methods: A total of 19 adult female Sprague−Dawley rats were induced with acute E. coli infection (n = 7), chronic E. coli infection (n = 6), or served as controls (n = 6). In each group, the profiles of p-CREB cell were counted in 6−10 sections of each of the DRG collected. DRG cells exhibiting intense nuclear staining were considered to be positive for p-CREB immunoreactivity (p-CREB-IR). Results: Overall, the immunoreactivity of p-CREB was examined in smaller cell profiles with nuclear staining or nuclear and cytoplasmic staining in the DRGs (L1−L6, S1). In the chronic cystitis group, p-CREB-IR in the L1−L6 and S1 DRG was significantly higher than the control group (p < 0.05). Further, p-CREB-IR in the L3−L6 and S1 DRG of the chronic cystitis group was significantly greater than that in the acute cystitis group (p < 0.05). In the control and acute cystitis groups, p-CREB-IR in the L4−L5 DRG was significantly lower than that found in the other DRG sections (p < 0.05). Conclusions: Altogether, acute or chronic E.coli cystitis changed the immunoreactivity of p-CREB in lumbosacral DRG cells. In particular, chronic E. coli infection triggered p-CREB overexpression in L1−L6 and S1 DRG, indicating subsequent pathologic changes.

Urine Nerve Growth Factor May Not Be Useful as a Biomarker of Overactive Bladder in Patients with Pelvic Organ Prolapse

(1) Background: Overactive bladder (OAB) symptoms are frequently present in women with pelvic organ prolapse (POP). Although urinary nerve growth factor (NGF) is a promising biomarker of OAB, little is known about its role in patients with OAB secondary to POP. The aim of the study was to evaluate urinary NGF levels in patients with POP involving the anterior vaginal wall and check if it may serve as a predicting factor for postoperative resolution of OAB symptoms. (2) Methods: Eighty-three Caucasian women included in the study were divided into three groups: pure OAB, one associated with POP (POP&OAB) and a control group composed of healthy volunteers. The urine NGF and creatinine were assessed with ELISA tests to calculate the NGF/creatinine ratio. (3) Results: The NGF/creatinine ratio was significantly higher in patients with pure OAB in comparison with other groups; however, it did not differ between the control group and the POP&OAB group. There was no correlation between NGF/creatinine ratio and age, menopausal status, BMI, parity or urodynamic findings. The NGF/creatinine ratio was not a prognostic factor for OAB symptoms' resolution after surgical treatment of POP. (4) Conclusions: Urinary NGF excretion is not increased in women with OAB secondary to POP; thus, it may not serve as an OAB biomarker in these patients.

Current knowledge and novel frontiers in lower urinary tract dysfunction after spinal cord injury: Basic research perspectives

This review article aims to summarize the recent advancement in basic research on lower urinary tract dysfunction (LUTD) following spinal cord injury (SCI) above the sacral level. We particularly focused on the neurophysiologic mechanisms controlling the lower urinary tract (LUT) function and the SCI-induced changes in micturition control in animal models of SCI. The LUT has two main functions, the storage and voiding of urine, that are regulated by a complex neural control system. This neural system coordinates the activity of two functional units in the LUT: the urinary bladder and an outlet including bladder neck, urethra, and striated muscles of the pelvic floor. During the storage phase, the outlet is closed and the bladder is quiescent to maintain a low intravesical pressure and continence, and during the voiding phase, the outlet relaxes and the bladder contracts to promote efficient release of urine. SCI impairs voluntary control of voiding as well as the normal reflex pathways that coordinate bladder and sphincter function. Following SCI, the bladder is initially areflexic but then becomes hyperreflexic due to the emergence of a spinal micturition reflex pathway. However, the bladder does not empty efficiently because coordination between the bladder and urethral sphincter is lost. In animal models of SCI, hyperexcitability of silent C-fiber bladder afferents is a major pathophysiological basis of neurogenic LUTD, especially detrusor overactivity. Reflex plasticity is associated with changes in the properties of neuropeptides, neurotrophic factors, or chemical receptors of afferent neurons. Not only C-fiber but also Aδ-fiber could be involved in the emergence of neurogenic LUTD such as detrusor sphincter dyssynergia following SCI. Animal research using disease models helps us to detect the different contributing factors for LUTD due to SCI and to find potential targets for new treatments.

Best practices for cystometric evaluation of lower urinary tract function in muriform rodents

AIMS

Rodent cystometry has provided valuable insights into the impact of the disease, injury, and aging on the cellular and molecular pathways, neurologic processes, and biomechanics of lower urinary tract function. The purpose of this white paper is to highlight the benefits and shortcomings of different experimental methods and strategies and to provide guidance on the proper interpretation of results.

METHODS

Literature search, selection of articles, and conclusions based on discussions among a panel of workers in the field.

RESULTS

A range of cystometric tests and techniques used to explore biological phenomena relevant to the lower urinary tract are described, the advantages and disadvantages of various experimental conditions are discussed, and guidance on the practical aspects of experimental execution and proper interpretation of results are provided.

CONCLUSIONS

Cystometric evaluation of rodents comprises an extensive collection of functional tests that can be performed under a variety of experimental conditions. Decisions regarding which approaches to choose should be determined by the specific questions to be addressed and implementation of the test should follow standardized procedures.

Therapeutic Effect of Botulinum Toxin A on Sensory Bladder Disorders-From Bench to Bedside

Bladder oversensitivity arises from several different conditions involving the bladder, bladder outlet, systemic or central nervous system diseases. Increase of the bladder sensation results from activation of the sensory receptors in the urothelial cells or suburothelial tissues. Medical treatment targeting the overactive bladder (OAB) or interstitial cystitis (IC) might relieve oversensitive bladder symptoms (frequency, urgency and pain) in a portion of patients, but a certain percentage of patients still need active management. Botulinum toxin A (BoNT-A) has been demonstrated to have anti-inflammatory and antinociceptive effects in bladder sensory disorders and has been shown effective in the reduction of bladder oversensitivity and the increase of functional bladder capacity. For patients with OAB, urgency and urinary incontinence improved, while in patients with IC, bladder pain could be relieved in association with reduction of bladder oversensitivity after BoNT-A intravesical injection. Histological evidence has confirmed the therapeutic mechanism and clinical efficacy of intravesical BoNT-A injection on patients with OAB or IC. Bladder oversensitivity can also be relieved with the instillation of liposome encapsulated BoNT-A or low energy show waves (LESWs), which enable the BoNT-A molecule to penetrate into the urothelium and suburothelial space without affecting the detrusor contractility. Liposome encapsulated BoNT-A or combined LESWs and BoNT-A instillation might be future treatment alternatives for bladder oversensitivity in sensory bladder disorders.

Clinical application of intravesical botulinum toxin type A for overactive bladder and interstitial cystitis

After decades of clinical and basic science research, the clinical application of botulinum toxin A (Botox) in urology has been extended to neurogenic detrusor overactivity (NDO), idiopathic detrusor overactivity, refractory overactive bladder (OAB), interstitial cystitis/bladder pain syndrome (IC/BPS), lower urinary tract symptoms, benign prostatic hyperplasia, and neurogenic or non-neurogenic lower urinary tract dysfunction in children. Botox selectively disrupts and modulates neurotransmission, suppresses detrusor overactivity, and modulates sensory function, inflammation, and glandular function. In addition to motor effects, Botox has been found to have sensory inhibitory effects and anti-inflammatory effects; therefore, it has been used to treat IC/BPS and OAB. Currently, Botox has been approved for the treatment of NDO and OAB. Recent clinical trials on Botox for the treatment of IC/BPS have reported promising therapeutic effects, including reduced bladder pain. Additionally, the therapeutic duration was found to be longer with repeated Botox injections than with a single injection. However, the use of Botox for IC/BPS has not been approved. This paper reviews the recent advances in intravesical Botox treatment for OAB and IC/BPS.

PACAP/PAC1 Expression and Function in Micturition Pathways

Neural injury, inflammation, or diseases commonly and adversely affect micturition reflex function that is organized by neural circuits in the CNS and PNS. One neuropeptide receptor system, pituitary adenylate cyclase-activating polypeptide (PACAP; Adcyap1), and its cognate receptor, PAC1 (Adcyap1r1), have tissue-specific distributions in the lower urinary tract. PACAP and associated receptors are expressed in the LUT and exhibit changes in expression, distribution, and function in preclinical animal models of bladder pain syndrome (BPS)/interstitial cystitis (IC), a chronic, visceral pain syndrome characterized by pain, and LUT dysfunction. Blockade of the PACAP/PAC1 receptor system reduces voiding frequency and somatic (e.g., hindpaw, pelvic) sensitivity in preclinical animal models and a transgenic mouse model that mirrors some clinical symptoms of BPS/IC. The PACAP/receptor system in micturition pathways may represent a potential target for therapeutic intervention to reduce LUT dysfunction following urinary bladder inflammation.

Pharmacological management of interstitial cystitis /bladder pain syndrome and the role cyclosporine and other immunomodulating drugs play

INTRODUCTION

Interstitial cystitis/bladder pain syndrome (IC/BPS) is a symptomatic disorder characterized by pelvic pain and urinary frequency. Immunological responses are considered as one of the possible etiologies of IC/BPS. In this review, we focused on emerging targets, especially on those modulating immunological mechanisms for the treatments of IC/BPS. Area covered: This review was based on the literature search of PubMed/MEDLINE, for which key words following bladder pain syndrome, interstitial cystitis, and/or cyclosporine A (CyA) were used. We discussed current treatments and the drugs targeting the immune responses including CyA and other drugs with different mechanisms including NGF antibodies and P2X3 antagonists. Expert commentary: IC/BPS is often difficult to treat by current treatments. Immunosuppression agents, especially CyA are considered as effective treatments for IC/BPS with Hunner's lesion because these drugs suppress the inflammatory responses in the bladder underlying urinary symptoms of the disease. Base on the previous literatures, we should use CyA for the refractory IC/BPS, especially that with Hunner's lesion due to its side effects. New drugs targeting other mechanisms such as urothelial or afferent nerve dysfunction or new delivery systems such as sustained drug releasing devices or gene therapy techniques may be promising for the future treatments of IC/BPS.

Botulinum toxin in the treatment of overactive bladder

Clinical effectiveness of botulinum toxin (BTX) in the treatment of both neurogenic and idiopathic detrusor overactivity has been demonstrated in several studies. However, different protocols and techniques have been used by authors.

Methods.

Literature review on intradetrusor injection of BTX for detrusor overactivity.

Results.

The greatest clinical experience reports the use of 200 and 300 U Botox®. Available data suggest that clinical efficacy, duration, and the side effect profile is similar at these doses. Very few data, on the other hand, are available regarding the clinical outcomes using the Dysport® preparation; isolated reports support that efficacy is similar when using a dosing range of 500 to 1000 SU with increased risk of systemic side effects using 1000 SU. A variety of injection volumes was used, demonstrating similar efficacy and tolerability profile. Clinical effect duration extends six to ten months in the majority of studies. Data suggest that a repeated injection scheme proves successful in the vast majority of initial responders.

Conclusions.

Safety, effectiveness, specificity and reversibility make BTX a new attractive treatment modality for overactive bladder syndrome. However, more experience is needed to standardize the injection protocol with respect to therapeutic outcomes and adverse effects.

Urinary Nerve Growth Factor as a Potential Biomarker of Treatment Outcomes in Overactive Bladder Patients

Purpose

The aim of this study was to investigate urinary nerve growth factor (NGF) as a biomarker of treatment efficacy and recurrence in overactive bladder (OAB) patients.

Methods

We enrolled 189 OAB subjects who visited our outpatient clinic from February 2010 to February 2015. All subjects with OAB received antimuscarinic treatment. A 3-day voiding diary and questionnaire were collected from each patient. Urinary levels of NGF were evaluated at baseline, the beginning of antimuscarinic treatment, and the end of antimuscarinic treatment. Urinary NGF was normalized to urine creatinine (Cr). Between-group comparisons of baseline characteristics were made using the Mann-Whitney U-test. Multivariate logistic regression analyses were used to predict responses to anticholinergic treatment and recurrence. The Wilcoxon signed-rank test with the Bonferroni correction was used for intragroup comparisons. A receiver operating characteristic curve was used to analyze the utility of this biomarker.

Results

Urinary levels of NGF/Cr tended to decrease in patients who responded to treatment (n=62), but this was not significant (P=0.260). Urinary NGF levels were higher at baseline in patients who did not experience recurrence than in those who did (P=0.047). In those who did not experience recurrence (n=29), urinary NGF/Cr decreased at the end of treatment compared to baseline, and this reduction was maintained at 12 weeks after the end of treatment (P<0.05).

Conclusions

Urinary NGF is a potential biomarker for predicting the outcome of antimuscarinic treatment in OAB patients. This may provide useful information when deciding to stop antimuscarinic treatment in responders.

PACAP/Receptor System in Urinary Bladder Dysfunction and Pelvic Pain Following Urinary Bladder Inflammation or Stress

Complex organization of CNS and PNS pathways is necessary for the coordinated and reciprocal functions of the urinary bladder, urethra and urethral sphincters. Injury, inflammation, psychogenic stress or diseases that affect these nerve pathways and target organs can produce lower urinary tract (LUT) dysfunction. Numerous neuropeptide/receptor systems are expressed in the neural pathways of the LUT and non-neural components of the LUT (e.g., urothelium) also express peptides. One such neuropeptide receptor system, pituitary adenylate cyclase-activating polypeptide (PACAP; Adcyap1) and its cognate receptor, PAC1 (Adcyap1r1), have tissue-specific distributions in the LUT. Mice with a genetic deletion of PACAP exhibit bladder dysfunction and altered somatic sensation. PACAP and associated receptors are expressed in the LUT and exhibit neuroplastic changes with neural injury, inflammation, and diseases of the LUT as well as psychogenic stress. Blockade of the PACAP/PAC1 receptor system reduces voiding frequency in preclinical animal models and transgenic mouse models that mirror some clinical symptoms of bladder dysfunction. A change in the balance of the expression and resulting function of the PACAP/receptor system in CNS and PNS bladder reflex pathways may underlie LUT dysfunction including symptoms of urinary urgency, increased voiding frequency, and visceral pain. The PACAP/receptor system in micturition pathways may represent a potential target for therapeutic intervention to reduce LUT dysfunction.

Pathomechanism of Interstitial Cystitis/Bladder Pain Syndrome and Mapping the Heterogeneity of Disease

Interstitial cystitis/bladder pain syndrome (IC/BPS) is a heterogeneous syndrome which is usually characterized by urinary frequency, nocturia, and bladder pain. Several pathomechanisms have been proposed, including uroepithelial dysfunction, mast cell activation, neurogenic inflammation, autoimmunity, and occult urinary tract infections. It is possible that an inflammatory process alters regulation of urothelial homeostasis and results in dysfunction of the bladder epithelium. Different phenotypes of IC/BPS have been explored including Hunner and non-Hunner type IC, hypersensitive bladder, and bladder pain both with and without functional somatic syndrome. Different gene expressions have also been found in different IC phenotypes. Abnormal expressions of uroplakin, chondroitin sulfate and adhesive protein E-cadherin, tight junction protein zonula occludens-1 in IC/BPS bladder suggest abnormal epithelial differentiation in this bladder disease. Analysis of inflammatory proteins, or cytokines in the urine or serum provides another diagnostic foundation forIC/BPS subtypes. The involvement of IC/BPS in systemic functional somatic syndrome and other pelvic organ diseases might also subdivide subtypes of IC/BPS. Chronic inflammation, increased urothelial apoptosis, and abnormal urothelial function are closely associated in IC bladders. This article reviews recent research on the pathomechanisms of IC, which might help us in mapping the heterogeneity of the disease.

Pathophysiology, Clinical Importance, and Management of Neurogenic Lower Urinary Tract Dysfunction Caused by Suprasacral Spinal Cord Injury

Management of persistent lower urinary tract dysfunction resulting from severe thoracolumbar spinal cord injury can be challenging. Severe suprasacral spinal cord injury releases the spinal cord segmental micturition reflex from supraspinal modulation and increases nerve growth factor concentration in the bladder wall, lumbosacral spinal cord, and dorsal root ganglion, which subsequently activates hypermechanosensitive C-fiber bladder wall afferents. Hyperexcitability of bladder afferents and detrusor overactivity can cause urine leaking during the storage phase. During urine voiding, the loss of supraspinal control that normally coordinates detrusor contraction with sphincter relaxation can lead to spinal cord segmental reflex-mediated simultaneous detrusor and sphincter contractions or detrusor-sphincter dyssynergia, resulting in inefficient urine voiding and high residual volume. These disease-associated changes can impact on the quality of life and life expectancy of spinal-injured animals. Here, we discuss the pathophysiology and management considerations of lower urinary tract dysfunction as the result of severe, acute, suprasacral spinal cord injury. In addition, drawing from experimental, preclinical, and clinical medicine, we introduce some treatment options for neurogenic lower urinary tract dysfunction that are designed to: (1) prevent urine leakage arising because of detrusor overactivity during bladder filling, (2) preserve upper urinary tract integrity and function by reducing intravesical pressure and subsequent vesicoureteral reflux, and (3) prevent urinary tract and systemic complications by treating and preventing urinary tract infections.

Effects of CYP-Induced Cystitis on Growth Factors and Associated Receptor Expression in Micturition Pathways in Mice with Chronic Overexpression of NGF in Urothelium

We have determined if cyclophosphamide (CYP)-induced cystitis produces additional changes in growth factor/receptors expression in the urinary bladder (urothelium, detrusor) and lumbosacral (L6-S1) dorsal root ganglia (DRG) in a transgenic mouse model with chronic urothelial overexpression of NGF (NGF-OE). Functionally, NGF-OE mice treated with CYP exhibit significant increases in voiding frequency above that observed in control NGF-OE mice (no CYP). Quantitative PCR was used to determine NGF, BDNF, VEGF, and receptors (TrkA, TrkB, p75(NTR)) transcripts expression in tissues from NGF-OE and wild-type (WT) mice with CYP-induced cystitis of varying duration (4 h, 48 h, 8 days). In urothelium of control NGF-OE mice, NGF mRNA was significantly (p ≤ 0.001) increased. Urothelial expression of NGF mRNA in NGF-OE mice treated with CYP (4 h, 48 h, 8 days) was not further increased but maintained with all durations of CYP treatment evaluated. In contrast, CYP-induced cystitis (4 h, 48 h, 8 days) in NGF-OE mice demonstrated significant (p ≤ 0.05) regulation in BDNF, VEGF, TrkA, TrkB, and P75(NTR) mRNA in urothelium and detrusor smooth muscle. Similarly, CYP-induced cystitis (4 h, 48 h, 8 days) in NGF-OE mice resulted in significant (p ≤ 0.05), differential changes in transcript expression for NGF, BDNF, and receptors (TrkA, TrkB, p75(NTR)) in S1 DRG that was dependent on the duration-of CYP-induced cystitis. In general, NGF, BDNF, TrkA, and TrkB protein content in the urinary bladder increased in WT and NGF-OE mice with CYP-induced cystitis (4 h). Changes in NGF, TrkA and TrkB expression in the urinary bladder were significantly (p ≤ 0.05) greater in NGF-OE mice with CYP-induced cystitis (4 h) compared to WT mice with cystitis (4 h). However, the magnitude of change between WT and NGF-OE mice was only significantly (p ≤ 0.05) different for TrkB expression in urinary bladder of NGF-OE mice treated with CYP. These studies are consistent with target-derived NGF and other inflammatory mediators affecting neurochemical plasticity with potential contributions to reflex function of micturition pathways.

Intravesical PAC1 Receptor Antagonist, PACAP(6-38), Reduces Urinary Bladder Frequency and Pelvic Sensitivity in NGF-OE Mice

Chronic NGF overexpression (OE) in the urothelium, achieved through the use of a highly urothelium-specific uroplakin II promoter, stimulates neuronal sprouting in the urinary bladder, produces increased voiding frequency and non-voiding contractions, and referred somatic sensitivity. Additional NGF-mediated pleiotropic changes might contribute to increased voiding frequency and pelvic hypersensitivity in NGF-OE mice such as neuropeptide/receptor systems including PACAP(Adcyap1) and PAC1 receptor (Adcyap1r1). Given the presence of PAC1-immunoreactive fibers and the expression of PAC1 receptor expression in bladder tissues, and PACAP-facilitated detrusor contraction, whether PACAP/receptor signaling contributes to increased voiding frequency and somatic sensitivity was evaluated in NGF-OE mice. Intravesical administration of the PAC1 receptor antagonist, PACAP(6-38) (300 nM), significantly (p ≤ 0.01) increased intercontraction interval (2.0-fold) and void volume (2.5-fold) in NGF-OE mice. Intravesical instillation of PACAP(6-38) also decreased baseline bladder pressure in NGF-OE mice. PACAP(6-38) had no effects on bladder function in WT mice. Intravesical administration of PACAP(6-38) (300 nM) significantly (p ≤ 0.01) reduced pelvic sensitivity in NGF-OE mice but was without effect in WT mice. PACAP/receptor signaling contributes to the increased voiding frequency and pelvic sensitivity observed in NGF-OE mice.

Effect of tibial nerve stimulation on bladder afferent nerve activity in a rat detrusor overactivity model

OBJECTIVES

To study the post-stimulation effect of tibial nerve stimulation on rat bladder afferent activity, and urodynamic parameters in normal and acetic acid-induced detrusor overactivity conditions.

METHODS

In urethane anesthetized male Wistar rats, the tibial nerve was stimulated for 30 min at 5 Hz, pulse width 200 μs and amplitude approximately threefold the threshold to induce a slight toe movement. The post-stimulation effect was studied by measuring afferent nerve activity of postganglionic pelvic nerve branches and various urodynamic parameters under two different conditions: (i) in physiological saline filling experiments (simulating normal bladder condition); and (ii) in acetic acid irritated bladders (simulating detrusor overactivity).

RESULTS

After 30 min of tibial nerve stimulation in saline filling experiments, the bladder capacity, threshold pressure and afferent nerve activity were not significantly different from the prestimulation measurements. The instillation of 0.5% acetic acid significantly reduced the bladder capacity and increased the afferent nerve activity. Tibial nerve stimulation significantly improved the bladder capacity and suppressed the afferent nerve activity compared with prestimulation acetic acid measurements.

CONCLUSIONS

Tibial nerve stimulation is able to significantly restore the bladder capacity by inhibiting afferent nerve activity in chemically irritated rat bladders. The present study provides important basic electrophysiological evidence to substantiate the clinical use of tibial nerve stimulation for treatment of symptoms related to detrusor overactivity.

Bladder afferent hyperexcitability in bladder pain syndrome/interstitial cystitis

Bladder pain syndrome/interstitial cystitis is a disease with lower urinary tract symptoms, such as bladder pain and urinary frequency, which results in seriously impaired quality of life of patients. The extreme pain and urinary frequency are often difficult to treat. Although the etiology of bladder pain syndrome/interstitial cystitis is still not known, there is increasing evidence showing that afferent hyperexcitability as a result of neurogenic bladder inflammation and urothelial dysfunction is important to the pathophysiological basis of symptom development. Further investigation of the pathophysiology will lead to the effective treatment of patients with bladder pain syndrome/interstitial cystitis.

Urinary bladder inflammation induces changes in urothelial nerve growth factor and TRPV1 channels

BACKGROUND AND PURPOSE

The urinary bladder urothelium expresses various receptors and in response to chemical and mechanical stimuli releases mediators, thereby modulating bladder sensory pathways. Transient receptor potential vanilloid 1 (TRPV1) ion channels and nerve growth factor (NGF) in those cells are implicated in this modulatory effect and play a role in sensitizing pain-related afferent pathways during inflammation. In this study, we investigated the interaction between NGF and TRPV1 channels in urothelial cells.

EXPERIMENTAL APPROACH

Urothelial cells from female Sprague-Dawley rat bladders were cultured to quantify membrane expression of TRPV1 channels and capsaicin-induced ATP release in the presence of NGF alone or with TrKA or PI3K inhibitors. Pain scores from rats with cyclophosphamide (CYP)-induced bladder inflammation were assessed after treatment with a TrkA antagonist. Bladders (from control and CYP rats) were collected and analysed for NGF content and TRPV1 channel expression.

KEY RESULTS

Cultured cells responded to NGF with increased TRPV1 channel expression in the cell membrane and increased release of ATP. Both responses were blocked by either a TrkA antagonist or a PI3K inhibitor. Treatment in vivo with the TrkA antagonist alleviated pain symptoms and reduced CYP-induced NGF overexpression in the mucosa. Furthermore, in urothelial cells from animals with bladder inflammation, expression of TRPV1 channels in the membrane was significantly increased.

CONCLUSIONS AND IMPLICATIONS

During bladder inflammation, increased production of NGF in urothelial cells induced increased expression and activity of TRPV1 channels in the cell membrane. This effect was primarily mediated by the PI3K pathway.

Activation of cannabinoid receptor 1 inhibits increased bladder activity induced by nerve growth factor

Nerve growth factor (NGF) is an important mediator of inflammatory pain, in part by sensitizing afferent nerve fibers, and expression of NGF is increased during bladder inflammation. We investigated whether intravesical instillation of the selective cannabinoid receptor 1 (CB1) agonist arachidonyl-2'-chloroethylamide (ACEA) affects NGF-induced increased bladder activity in female C57BL/6J wild-type (WT) mice. We also examined the effects of intravesical NGF in female fatty acid amide hydrolase knock-out (FAAH KO) mice. We found that CB1 and tyrosine kinase A (trkA, the high-affinity NGF receptor) were present in L6 dorsal root ganglion (DRG) afferent neurons and in bladders of both genotypes. Intravesical NGF increased bladder activity that was inhibited by intravesical ACEA in WT mice. The inhibitory effects of ACEA were reversed by the selective CB1 antagonist AM 251. Intravesical NGF failed to affect bladder activity in FAAH KO mice, and treatment with AM251, restored the stimulatory effects of NGF on the bladder in FAAH KO mice. These results indicate that activation of CB1 inhibits increased bladder activity induced by NGF.

Neural control of the lower urinary tract

This article summarizes anatomical, neurophysiological, pharmacological, and brain imaging studies in humans and animals that have provided insights into the neural circuitry and neurotransmitter mechanisms controlling the lower urinary tract. The functions of the lower urinary tract to store and periodically eliminate urine are regulated by a complex neural control system in the brain, spinal cord, and peripheral autonomic ganglia that coordinates the activity of smooth and striated muscles of the bladder and urethral outlet. The neural control of micturition is organized as a hierarchical system in which spinal storage mechanisms are in turn regulated by circuitry in the rostral brain stem that initiates reflex voiding. Input from the forebrain triggers voluntary voiding by modulating the brain stem circuitry. Many neural circuits controlling the lower urinary tract exhibit switch-like patterns of activity that turn on and off in an all-or-none manner. The major component of the micturition switching circuit is a spinobulbospinal parasympathetic reflex pathway that has essential connections in the periaqueductal gray and pontine micturition center. A computer model of this circuit that mimics the switching functions of the bladder and urethra at the onset of micturition is described. Micturition occurs involuntarily in infants and young children until the age of 3 to 5 years, after which it is regulated voluntarily. Diseases or injuries of the nervous system in adults can cause the re-emergence of involuntary micturition, leading to urinary incontinence. Neuroplasticity underlying these developmental and pathological changes in voiding function is discussed.

Urinary nerve growth factor could be a biomarker for interstitial cystitis/painful bladder syndrome: a meta-analysis

To examine whether urinary nerve growth factor (NGF) could serve as a biomarker for interstitial cystitis/painful bladder syndrome (IC/PBS), we conducted a comprehensive meta-analysis of 9 studies. Among the studies considered, patients with IC/PBS had higher urinary NGF and NGF/Cr levels compared to those of healthy people (SMD = 1.94, 95%CI = 0.79-3.08, P = 0.0009 and SMD = 1.79, 95%CI = 0.65-2.93, P = 0.002, respectively). In addition, there was a significant difference between patients with IC/PBS and patients with overactive bladder (OAB) symptoms with respect to the urinary NGF and NGF/Cr levels (SMD = -0.62, 95%CI = -1.00--0.24, P = 0.001 and SMD = -0.70, 95%CI = -1.01--0.39, P<0.0001, respectively). Furthermore, patients had a significantly lower urinary NGF level after successful treatment (SMD = 1.74, 95%CI = 0.32-3.17, P = 0.02). In conclusion, urinary NGF could be a useful biomarker for the diagnosis of OAB, a urinary biomarker for the differential diagnosis of IC/PBS and OAB (when a critical urinary NGF or NGF/Cr level is needed), and a predictive biomarker to help guide treatment.

Social stress induces changes in urinary bladder function, bladder NGF content, and generalized bladder inflammation in mice

Social stress may play a role in urinary bladder dysfunction in humans, but the underlying mechanisms are unknown. In the present study, we explored changes in bladder function caused by social stress using mouse models of stress and increasing stress. In the stress paradigm, individual submissive FVB mice were exposed to C57BL/6 aggressor mice directly/indirectly for 1 h/day for 2 or 4 wk. Increased stress was induced by continuous, direct/indirect exposure of FVB mice to aggressor mice for 2 wk. Stressed FVB mice exhibited nonvoiding bladder contractions and a decrease in both micturition interval (increased voiding frequency) and bladder capacity compared with control animals. ELISAs demonstrated a significant increase in histamine protein expression with no change in nerve growth factor protein expression in the urinary bladder compared with controls. Unlike stressed mice, mice exposed to an increased stress paradigm exhibited increased bladder capacities and intermicturition intervals (decreased voiding frequency). Both histamine and nerve growth factor protein expression were significantly increased with increased stress compared with control bladders. The change in bladder function from increased voiding frequency to decreased voiding frequency with increased stress intensity suggests that changes in social stress-induced urinary bladder dysfunction are context and duration dependent. In addition, changes in the bladder inflammatory milieu with social stress may be important contributors to changes in urinary bladder function.

Acupuncture versus solifenacin for treatment of overactive bladder and its correlation with urine nerve growth factor levels: a randomized, placebo-controlled clinical trial

OBJECTIVE

To determine whether acupuncture is effective as an overactive bladder (OAB) treatment compared with solifenacin and placebo, and to investigate its relation with urine nerve growth factor (NGF) levels.

PATIENTS AND METHODS

The study was conducted with methodological rigor based on the Consolidated Standards of Reporting Trials criteria. 90 female patients with OAB were included and randomly assigned to a solifenacin, acupuncture or placebo group. The medicated group received solifenacin 5 mg/day; the acupuncture and placebo groups were treated twice a week for 4 weeks. Symptom scores, quality of life scores, frequency of micturition and urine NGF levels were used to assess treatment efficiency.

RESULTS

The study was completed with 82 patients (n = 30 in the solifenacin group, n = 28 in the acupuncture group and n = 24 in the placebo group). After treatment, comparison of the medical and acupuncture therapy groups with the placebo group showed significant differences between recovery concerning quality of life (p < 0.001 and p < 0.01, respectively) and symptom scores (p < 0.001 and p < 0.001, respectively). The decrease of NGF levels after treatment compared to before treatment was determined in each group (solifenacin, acupuncture, placebo group; p < 0.001, p < 0.001, p = 0.359, respectively). Sufficient symptomatic improvement was not achieved in 8 patients in the acupuncture group. Therefore, comparisons were assessed twice with and without including these patients, and NGF levels in the acupuncture group were higher than at first comparison in which all patients in the acupuncture group were included.

CONCLUSIONS

In patients with OAB in whom anticholinergic treatment is contraindicated, acupuncture may be considered another treatment option.

Neural control of lower urinary tract and targets for pharmacological therapy

Studies on the physiology and pharmacology of the lower urinary tract have brought new information and concepts about the complex neural control of micturition. There are many mechanisms, some proven and others not yet completely understood, in which pharmacological agents may act facilitating the filling, storage, and emptying of the bladder. This review describes the peripheral innervation and the main pathways involved in lower urinary tract control. It also presents potential targets for the treatment of voiding dysfunctions.

Intravesical TRPV4 blockade reduces repeated variate stress-induced bladder dysfunction by increasing bladder capacity and decreasing voiding frequency in male rats

Individuals with functional lower urinary tract disorders including interstitial cystitis (IC)/bladder pain syndrome (BPS) and overactive bladder (OAB) often report symptom (e.g., urinary frequency) worsening due to stress. One member of the transient receptor potential ion channel vanilloid family, TRPV4, has recently been implicated in urinary bladder dysfunction disorders including OAB and IC/BPS. These studies address the role of TRPV4 in stress-induced bladder dysfunction using an animal model of stress in male rats. To induce stress, rats were exposed to 7 days of repeated variate stress (RVS). Quantitative PCR data demonstrated significant (P ≤ 0.01) increases in TRPV4 transcript levels in urothelium but not detrusor smooth muscle. Western blot analyses of split urinary bladders (i.e., urothelium and detrusor) showed significant (P ≤ 0.01) increases in TRPV4 protein expression levels in urothelial tissues but not detrusor smooth muscle. We previously showed that RVS produces bladder dysfunction characterized by decreased bladder capacity and increased voiding frequency. The functional role of TRPV4 in RVS-induced bladder dysfunction was evaluated using continuous, open outlet intravesical infusion of saline in conjunction with administration of a TRPV4 agonist, GSK1016790A (3 μM), a TRPV4 antagonist, HC067047 (1 μM), or vehicle (0.1% DMSO in saline) in control and RVS-treated rats. Bladder capacity, void volume, and intercontraction interval significantly decreased following intravesical instillation of GSK1016790A in control rats and significantly (P ≤ 0.01) increased following administration of HC067047 in RVS-treated rats. These results demonstrate increased TRPV4 expression in the urothelium following RVS and that TRPV4 blockade ameliorates RVS-induced bladder dysfunction consistent with the role of TRPV4 as a promising target for bladder function disorders.

Bladder sensory physiology: neuroactive compounds and receptors, sensory transducers, and target-derived growth factors as targets to improve function

Urinary bladder dysfunction presents a major problem in the clinical management of patients suffering from pathological conditions and neurological injuries or disorders. Currently, the etiology underlying altered visceral sensations from the urinary bladder that accompany the chronic pain syndrome, bladder pain syndrome (BPS)/interstitial cystitis (IC), is not known. Bladder irritation and inflammation are histopathological features that may underlie BPS/IC that can change the properties of lower urinary tract sensory pathways (e.g., peripheral and central sensitization, neurochemical plasticity) and contribute to exaggerated responses of peripheral bladder sensory pathways. Among the potential mediators of peripheral nociceptor sensitization and urinary bladder dysfunction are neuroactive compounds (e.g., purinergic and neuropeptide and receptor pathways), sensory transducers (e.g., transient receptor potential channels) and target-derived growth factors (e.g., nerve growth factor). We review studies related to the organization of the afferent limb of the micturition reflex and discuss neuroplasticity in an animal model of urinary bladder inflammation to increase the understanding of functional bladder disorders and to identify potential novel targets for development of therapeutic interventions. Given the heterogeneity of BPS/IC and the lack of consistent treatment benefits, it is unlikely that a single treatment directed at a single target in micturition reflex pathways will have a mass benefit. Thus, the identification of multiple targets is a prudent approach, and use of cocktail treatments directed at multiple targets should be considered.

Urinary nerve growth factor correlates with the severity of urgency and pain

INTRODUCTION AND HYPOTHESIS

Urinary nerve-growth-factor (NGF) level reflected the severity of urgency in patients with lower urinary tract symptoms (LUTS) and pain in patients with Bladder pain syndrome/interstitial cystitis (BPS/IC). The aim of this study was to investigate the levels of biomarkers, nerve growth factor (NGF), and prostaglandin E2 (PGE2) among disease groups sharing similar urinary symptoms and to elucidate which symptoms are related to individual biomarker levels.

METHODS

We studied 83 patients with LUTS who visited our outpatient clinic from May 2011 to December 2012. On the basis of clinical symptoms and a 3-day voiding diary, patients were classified into three groups: those with frequency (n = 13), overactive bladder (OAB) (n = 35), and BPS/IC (n = 35). Patients with stress urinary incontinence (SUI) or microscopic hematuria served as controls (n = 24). Storage symptoms were evaluated based on OAB symptom score (OAB-SS).

RESULTS

Mean patient age was 62.08 ± 11.47 (range, 23-84). Urinary NGF and creatinine-normalized NGF levels were significantly increased in those with OAB (201.90 and 4.08, respectively) and BPS/IC (173.71 and 2.72) compared with controls (77.77 and 1.29) and those with frequency (67.76 and 1.23). Neither value significantly differed between OAB and BPS/IC patients or between controls and frequency patients. Urinary PGE2 and creatinine-normalized PGE2 levels were not significantly different among groups. On linear regression analysis, urinary NGF levels were significantly correlated with urgency severity overall (R = 0.222) and also pain in BPS/IC patients (R = 0.409).

CONCLUSIONS

The levels of urinary NGF were elevated in patients with OAB and BPS/IC but not those with frequency and reflected the severity of urgency. In BPS/IC patients, urinary NGF increased with pain severity.

Effect of inflammatory mediators on ATP release of human urothelial RT4 cells

Inflammation is an important contributor to the aetiology of a number of bladder dysfunctions including interstitial cystitis, painful bladder syndrome, and overactive bladder. The aim of this study was to examine the effects of inflammatory mediators on urothelial ATP release. Human urothelial RT4 cells were exposed to normal buffer or varying concentrations of inflammatory mediators (bradykinin, histamine, and serotonin) in the presence or absence of hypotonic stretch stimuli (1 : 2 dilution of Krebs-Henseleit buffer). Others have demonstrated that bradykinin increased stretch-induced ATP release; however, we observed no change in control or stretch-induced ATP release with bradykinin. Pretreatment of RT4 cells with histamine or serotonin decreased stretch-induced ATP release (P = 0.037, P = 0.040, resp.). Previous studies have demonstrated increased ATP release in response to inflammation utilising whole bladder preparations in contrast to our simple model of cultured urothelial cells. The current study suggests that it is unlikely that there is a direct interaction between the release of inflammatory mediators and increased ATP release, but rather more complex interactions occurring in response to inflammation that lead to increased bladder sensation.

Neural mechanisms underlying lower urinary tract dysfunction

This article summarizes anatomical, neurophysiological, and pharmacological studies in humans and animals to provide insights into the neural circuitry and neurotransmitter mechanisms controlling the lower urinary tract and alterations in these mechanisms in lower urinary tract dysfunction. The functions of the lower urinary tract, to store and periodically release urine, are dependent on the activity of smooth and striated muscles in the bladder, urethra, and external urethral sphincter. During urine storage, the outlet is closed and the bladder smooth muscle is quiescent. When bladder volume reaches the micturition threshold, activation of a micturition center in the dorsolateral pons (the pontine micturition center) induces a bladder contraction and a reciprocal relaxation of the urethra, leading to bladder emptying. During voiding, sacral parasympathetic (pelvic) nerves provide an excitatory input (cholinergic and purinergic) to the bladder and inhibitory input (nitrergic) to the urethra. These peripheral systems are integrated by excitatory and inhibitory regulation at the levels of the spinal cord and the brain. Therefore, injury or diseases of the nervous system, as well as disorders of the peripheral organs, can produce lower urinary tract dysfunction, leading to lower urinary tract symptoms, including both storage and voiding symptoms, and pelvic pain. Neuroplasticity underlying pathological changes in lower urinary tract function is discussed.

Repeated variate stress in male rats induces increased voiding frequency, somatic sensitivity, and urinary bladder nerve growth factor expression

Stress exacerbates symptoms of functional lower urinary tract disorders including interstitial cystitis (IC)/bladder pain syndrome (BPS) and overactive bladder (OAB) in humans, but mechanisms contributing to symptom worsening are unknown. These studies address stress-induced changes in the structure and function of the micturition reflex using an animal model of stress in male rats. Rats were exposed to 7 days of repeated variate stress (RVS). Target organ (urinary bladder, thymus, adrenal gland) tissues were collected and weighed following RVS. Evans blue (EB) concentration and histamine, myeloperoxidase (MPO), nerve growth factor (NGF), brain-derived neurotropic factor (BDNF), and CXCL12 protein content (ELISA) were measured in the urinary bladder, and somatic sensitivity of the hindpaw and pelvic regions was determined following RVS. Bladder function was evaluated using continuous, open outlet intravesical infusion of saline in conscious rats. Increases in body weight gain were significantly (P ≤ 0.01) attenuated by day 5 of RVS, and adrenal weight was significantly (P ≤ 0.05) increased. Histamine, MPO, NGF, and CXCL12 protein expression was significantly (P ≤ 0.01) increased in the urinary bladder after RVS. Somatic sensitivity of the hindpaw and pelvic regions was significantly (P ≤ 0.01) increased at all monofilament forces tested (0.1-4 g) after RVS. Intercontraction interval, infused volume, and void volume were significantly (P ≤ 0.01) decreased after RVS. These studies demonstrate increased voiding frequency, histamine, MPO, NGF, and CXCL12 bladder content and somatic sensitivity after RVS suggesting an inflammatory component to stress-induced changes in bladder function and somatic sensitivity.

Highlights in basic autonomic neuroscience: contribution of the urothelium to sensory mechanisms in the urinary bladder

Urothelial cells in the urinary bladder express neural properties including: (1) release of neurotransmitters and neurotrophic factors, (2) expression of neurotransmitter receptors and ion channels, and (3) sensitivity to mechanical and chemical stimuli. These properties have focused attention on the possible contribution of the urothelium to the storage and emptying functions of the bladder. In addition chemicals released from urothelial cells can affect the excitability of adjacent afferent nerves and this interaction can be affected by pathological conditions. This raises the possibility that abnormal urothelial-afferent interactions may contribute to bladder dysfunctions and therefore be a target for drug therapy.

Changes in nerve growth factor level and symptom severity following antibiotic treatment for refractory overactive bladder

INTRODUCTION AND HYPOTHESIS

Overactive bladder (OAB) has a multifactorial aetiology, and for some women symptoms may be associated with chronic urothelial inflammation secondary to bacterial colonisation. One marker of such inflammation may be urinary nerve growth factor (NGF). We hypothesised that for women with OAB and urothelial inflammation, urinary NGF would be reduced following antibiotic therapy.

METHODS

Women with overactive bladder and urodynamic diagnosis of detrusor overactivity who were refractory to anticholinergics, and had histological evidence of urothelial inflammation were treated with a 6-week course of rotating antibiotics. Urinary NGF was measured by ELISA before and after treatment. Three-day bladder diaries, the Patients' Perception of Intensity of Urgency Scale, the King's Health Questionnaire and the Patients' Perception of Bladder Condition questionnaire were used to assess subjective and objective outcomes of therapy.

RESULTS

Thirty-nine women with refractory DO were recruited. The NGF levels decreased significantly after antibiotic therapy (Wilcoxon signed rank test; p = 0.015). There were significant improvements in daytime frequency, nocturia and urgency (p < 0.05), and 74 % of women reported improvement in perception of their bladder condition.

CONCLUSIONS

Urinary NGF is responsive to antibiotic therapy. Women with refractory overactive bladder and elevated NGF may benefit from antibiotic treatment.

Inhibitory effect of somatostatin receptor subtype-4 agonist NNC 26-9100 on micturition reflex in rats

OBJECTIVE

To investigate the effects of activation of somatostatin subtype 4 (SST4) on the micturition reflex in rats.

METHODS

Continuous cystometrograms (0.04 mL/min infusion rate) were performed in female Sprague-Dawley rats (242-265 g) under urethane anesthesia. After stable micturition cycles were established, a selective SST4 receptor agonist, NNC 26-9100, was administered intravenously in normal rats or rats pretreated with capsaicin 4 days before the experiments. The micturition parameters were recorded and compared before and after drug administration.

RESULTS

Intravenous administration of NNC 26-9100 (10-300 μg/kg) significantly increased the intercontraction interval in a dose-dependent fashion. Intravenous administration of NNC 26-9100 (10-300 μg/kg) also significantly increased the pressure threshold in a dose-dependent fashion. No significant changes were seen in the baseline pressure, maximum voiding pressure, or postvoid residual urine volume. However, NNC 26-9100-induced increases in the intercontraction intervals and pressure threshold were not seen in rats with C-fiber desensitization induced by capsaicin pretreatment.

CONCLUSION

These results indicate that in urethane-anesthetized rats, activation of the SST4 receptor can inhibit the micturition reflex by suppression of capsaicin-sensitive C-fiber afferent pathways. Thus, the SST4 receptor could be a potential target for the treatment of C-fiber afferent-mediated bladder dysfunction.

Role for pAKT in rat urinary bladder with cyclophosphamide (CYP)-induced cystitis

AKT phosphorylation following peripheral nerve injury or inflammation may play a role in somatic pain processes and visceral inflammation. To examine such a role in micturition reflexes with bladder inflammation, we induced bladder inflammation in adult female Wistar rats (200-300 g) by injecting cyclophosphamide (CYP) intraperitoneally at acute (150 mg/kg; 4 h), intermediate (150 mg/kg; 48 h), and chronic (75 mg/kg; every third day for 10 days) time points. Western blot analyses of whole urinary bladders showed significant increases (P ≤ 0.01) in phosphorylated (p) AKT at all time points; however, the magnitude of AKT phosphorylation varied with duration of CYP treatment. Immunohistochemical analyses of pAKT immunoreactivity (pAKT-IR) in cryostat bladder sections demonstrated duration-dependent, significant (P ≤ 0.01) increases in pAKT-IR in both the urothelium and detrusor smooth muscle of CYP-inflamed bladders. Additionally, a suburothelial population of pAKT-IR macrophages (CD68-, MAC2-, and F4/80-positive) was present in chronic CYP-treated bladders. The functional role of pAKT in micturition was evaluated using open, conscious cystometry with continuous instillation of saline in conjunction with administration of an inhibitor of AKT phosphorylation, deguelin (1.0 μg/10 μl), or vehicle (1% DMSO in saline) in control (no inflammation) and CYP (48 h)-treated rats. Bladder capacity, void volume, and intercontraction void interval increased significantly (P ≤ 0.05) following intravesical instillation of deguelin in CYP (48 h)-treated rats. These results demonstrate increased AKT phosphorylation in the urinary bladder with urinary bladder inflammation and that blockade of AKT phosphorylation in the urothelium improves overall bladder function.

Biomarkers in overactive bladder: a new objective and noninvasive tool?

Overactive bladder syndrome (OAB) is a highly prevalent urinary dysfunction, with considerable economic and human costs. Clinical diagnosis of OAB is still based on subjective symptoms. A new accurate, objective and noninvasive test to diagnose OAB and assess therapeutic outcome is lacking. Recent studies in lower urinary tract (LUT) dysfunctions, particularly in OAB patients, indicate that urinary proteins (neurotrophins, prostaglandins, and cytokines), serum C reactive protein, and detrusor wall thickness are altered, and such changes could be used as biomarkers of the disease. Nowadays, increasing emphasis has been given to the role of urinary neurotrophins, namely nerve growth factor (NGF) and brain derived neurotrophic factor (BDNF), as key players in some urinary dysfunctions. Although recently considered to be a bladder dysfunction biomarker, urinary NGF presents low sensitivity and specificity. Preliminary results suggest that BDNF may serve as a more efficient biomarker. Even though we have to wait for future studies to confirm the potential role of NGF and BDNF as OAB biomarkers, it is already clear that neurotrophins will contribute to elucidate the physiopathological basis of OAB. Herein are reviewed the latest advances in this new and exciting field, the detection and clinical application of emerging OAB biomarkers.

Plasticity in reflex pathways to the lower urinary tract following spinal cord injury

The lower urinary tract has two main functions, storage and periodic expulsion of urine, that are regulated by a complex neural control system in the brain and lumbosacral spinal cord. This neural system coordinates the activity of two functional units in the lower urinary tract: (1) a reservoir (the urinary bladder) and (2) an outlet (consisting of bladder neck, urethra and striated muscles of the external urethra sphincter). During urine storage the outlet is closed and the bladder is quiescent to maintain a low intravesical pressure. During micturition the outlet relaxes and the bladder contracts to promote efficient release of urine. This reciprocal relationship between bladder and outlet is generated by reflex circuits some of which are under voluntary control. Experimental studies in animals indicate that the micturition reflex is mediated by a spinobulbospinal pathway passing through a coordination center (the pontine micturition center) located in the rostral brainstem. This reflex pathway is in turn modulated by higher centers in the cerebral cortex that are involved in the voluntary control of micturition. Spinal cord injury at cervical or thoracic levels disrupts voluntary control of voiding as well as the normal reflex pathways that coordinate bladder and sphincter function. Following spinal cord injury the bladder is initially areflexic but then becomes hyperreflexic due to the emergence of a spinal micturition reflex pathway. However the bladder does not empty efficiently because coordination between the bladder and urethral outlet is lost. Studies in animals indicate that dysfunction of the lower urinary tract after spinal cord injury is dependent in part on plasticity of bladder afferent pathways as well as reorganization of synaptic connections in the spinal cord. Reflex plasticity is associated with changes in the properties of ion channels and electrical excitability of afferent neurons and appears to be mediated in part by neurotrophic factors released in the spinal cord and/or the peripheral target organs.

Promise of Urinary Nerve Growth Factor for Assessment of Overactive Bladder Syndrome

Overactive bladder syndrome (OAB) is highly prevalent bladder disorder in men and women. About 10-15% of the population suffers from urgency frequency with or without urgency urinary incontinence. It is estimated that 50-75% of patients with OAB may have urodynamic detrusor overactivity (DO). Urodynamic study invasive and most of the OAB patients might not accept it as a routine assessment. Therefore, a more objective and non-invasive test for diagnosis and assessing DO from OAB patients is needed. Recently, urinary nerve growth factor (NGF) has gained great interest in detecting DO in patients with OAB. Urinary NGF level was found to increase in OAB and urodynamic DO. Urinary NGF levels correlated with severity of OAB symptoms. Patients with either idiopathic or neurogenic DO may have increased urinary NGF levels. Urinary NGF levels have been shown to decrease in patients with patients with OAB and DO who have been well treated with antimuscarinics or botulinum toxin injection, but not in those with persistent OAB after treatment. Not all patients with OAB can have an elevated urinary NGF level; it may also be increased in patients with interstitial cystitis/painful bladder syndrome and other lower urinary tract diseases, suggesting urinary NGF expression could be a product of bladder inflammation and a limited specificity of urinary NGF for diagnosing DO. The source of urinary NGF has not yet been fully explored yet. Nevertheless, urinary NGF level is likely to be a promising biomarker for diagnosis of DO from OAB patients, to monitor therapeutic outcome and predict disease progression.