Enhanced ATP release from rat bladder urothelium during chronic bladder inflammation: Effect of botulinum toxin A

Cellular and molecular mechanisms involved in the analgesic effects of botulinum neurotoxin: A literature review

Botulinum neurotoxins (BoNTs), derived from Clostridium botulinum, have been employed to treat a range of central and peripheral neurological disease. Some studies indicate that BoNT may be beneficial for pain conditions as well. It has been hypothesized that BoNTs may exert their analgesic effects by preventing the release of pain-related neurotransmitters and neuroinflammatory agents from sensory nerve endings, suppressing glial activation, and inhibiting the transmission of pain-related receptors to the neuronal cell membrane. In addition, there is evidence to suggest that the central analgesic effects of BoNTs are mediated through their retrograde axonal transport. The purpose of this review is to summarize the experimental evidence of the analgesic functions of BoNTs and discuss the cellular and molecular mechanisms by which they can act on pain conditions. Most of the studies reviewed in this article were conducted using BoNT/A. The PubMed database was searched from 1995 to December 2022 to identify relevant literature.

The association of urinary BDNF, ATP, and MMP-2 with bladder compliance in children with myelodysplasia

AIM

The purpose of our study was to evaluate the relationship of urinary brain-derived neurotrophic factor (BDNF), adenosine triphosphate (ATP), matrix metallopreteinase-2 (MMP-2) with urodynamic findings and upper urinary tract deterioration (UUTD) in children with myelodysplasia.

MATERIALS AND METHODS

Children with myelodysplasia evaluated in outpatient clinic between 2022 and 2023 were included. All patients underwent urinary ultrasonography, voiding cystourethrography, urodynamics, and DMSA scintigraphy. Urine samples were collected before urodynamics. Control urine was collected from 10 healthy children. Urinary biomarker values of patients and controls were compared, and subgroup analysis was performed.

RESULTS

The median age of 40 children (26 girls) included in the study was 108 (8-216) months, and the control group (six girls) was 120 (60-154) (p = 0.981). Urinary BDNF, MMP-2, and ATP were found to be significantly higher in children with myelodysplasia compared to the control (p = 0.007, p = 0.027, p = 0.014, respectively). The three biomarker values were similar in children with bladder compliance below or above 10 cmH2O/mL (p = 0.750, p = 0.844, p = 0.575). No difference was found in terms of UUTD in all three biomarkers (p = 0.387, p = 0.892, p = 0.705). A negative correlation was found between urinary ATP and compliance (p < 0.05).

CONCLUSION

In this study, all three biomarkers were found to be higher in children with myelodysplasia than in controls. There was a negative correlation between urinary ATP and compliance. Urinary biomarkers may contribute the follow-up of children with neurogenic lower urinary tract deterioration in future with their noninvasive features. However, the lack of standardization and the inability to reliably predict risky groups are important shortcomings of urinary biomarkers.

Differential Influences of Endogenous and Exogenous Sensory Neuropeptides on the ATP Metabolism by Soluble Ectonucleotidases in the Murine Bladder Lamina Propria

Bladder urothelium and suburothelium/lamina propria (LP) have prominent sensory and transducer functions with the active participation of afferent neurons and urothelium-derived purine mediators such as adenosine 5'-triphosphate (ATP), adenosine 5'-diphosphate (ADP), and adenosine (ADO). Effective concentrations of purines at receptor targets depend significantly on the extracellular degradation of ATP by ectonucleotidases (ENTDs). We recently reported the regulated release of soluble ENTDs (s-ENTDs) in the LP and the consequent degradation of ATP to ADP, AMP, and ADO. Afferent neurons in the LP can be activated by urothelial ATP and release peptides and other transmitters that can alter the activity of cells in their vicinity. Using a murine decentralized ex vivo detrusor-free bladder model, 1,N6-etheno-ATP (eATP) as substrate, and sensitive HPLC-FLD methodologies, we found that exogenous neuropeptides calcitonin gene-related peptide (CGRP), substance P (Sub P), neurokinin A (NKA), and pituitary adenylate cyclase-activating polypeptide [PACAP (1-38)] all increased the degradation of eATP by s-ENTDs that were released in the LP spontaneously and/or during bladder filling. Using antagonists of neuropeptide receptors, we observed that endogenous NKA did not modify the ATP hydrolysis by s-ENTDs, whereas endogenous Sub P increased both the constitutive and distention-induced release of s-ENTDs. In contrast, endogenous CGRP and PACAP (1-38) increased the distention-induced, but not the spontaneous, release of s-ENTDs. The present study puts forward the novel idea that interactions between peptidergic and purinergic signaling mechanisms in the LP have an impact on bladder excitability and functions by regulating the effective concentrations of adenine purines at effector cells in the LP.

The Pannexin 1 Channel and the P2X7 Receptor Are in Complex Interplay to Regulate the Release of Soluble Ectonucleotidases in the Murine Bladder Lamina Propria

The bladder urothelium releases ATP into the lamina propria (LP) during filling, which can activate P2X receptors on afferent neurons and trigger the micturition reflex. Effective ATP concentrations are largely dependent on metabolism by membrane-bound and soluble ectonucleotidases (s-ENTDs), and the latter are released in the LP in a mechanosensitive manner. Pannexin 1 (PANX1) channel and P2X7 receptor (P2X7R) participate in urothelial ATP release and are physically and functionally coupled, hence we investigated whether they modulate s-ENTDs release. Using ultrasensitive HPLC-FLD, we evaluated the degradation of 1,N6-etheno-ATP (eATP, substrate) to eADP, eAMP, and e-adenosine (e-ADO) in extraluminal solutions that were in contact with the LP of mouse detrusor-free bladders during filling prior to substrate addition, as an indirect measure of s-ENDTS release. Deletion of Panx1 increased the distention-induced, but not the spontaneous, release of s-ENTDs, whereas activation of P2X7R by BzATP or high concentration of ATP in WT bladders increased both. In Panx1-/- bladders or WT bladders treated with the PANX1 inhibitory peptide 10Panx, however, BzATP had no effect on s-ENTDS release, suggesting that P2X7R activity depends on PANX1 channel opening. We concluded, therefore, that P2X7R and PANX1 are in complex interaction to regulate s-ENTDs release and maintain suitable ATP concentrations in the LP. Thus, while stretch-activated PANX1 hinders s-ENTDS release possibly to preserve effective ATP concentration at the end of bladder filling, P2X7R activation, presumably in cystitis, would facilitate s-ENTDs-mediated ATP degradation to counteract excessive bladder excitability.

Botulinum Toxin Therapy for Bladder Pain Syndrome/Interstitial Cystitis

Purpose of Review

Bladder pain syndrome (BPS)/interstitial cystitis (IC) can also be classified as either non-ulcerative or ulcerative, corresponding to the characteristic cystoscopic findings under hydrodistention. Promising therapeutic effects, including decreased bladder pain, have been reported from recent clinical trials using botulinum toxin A (BoNTA) for the treatment of BPS/IC. This review summarizes the current state of the literature on the underlying mechanisms of BoNTA therapy in BPS/IC as well as new forms of its application.

Recent Findings

BoNTA has its effect in the central nervous system in the afferent nerves as well as in the bladder wall. Besides the well-known effects of BoNTA in the nervous system, pain control as well as reduction of urinary urgency in BPS patients could be achieved by mast cell stabilization effecting histamine release as well as modulation of TRPV and PGE2 pathways, among other systems. In addition, new forms of BoNTA administration have focused on intravesical instillation of the drug in order to circumvent bladder wall injections. Hyperthermia, intravesical hydrogel, and lysosomes have been studied as new ways of BoNTA application in BPS/IC patients. From the available studies, bladder instillation of BoNTA in combination with EMDA is the most promising and effective novel approach.

Summary

The most promising novel application methods for BoNTA in patient with BPS/IC are bladder instillations. Future research needs to point out if bladder instillations with BoNTA with some form of bladder absorption enhancement such as hyperthermia or EMDA would be able to replace BoNTA injections in patients with BPS/IC

Effects of Intravesical Electrical Stimulation on Urinary Adenosine Triphosphate and Nitric Oxide in Rats With Detrusor Underactivity Induced By Bilateral Pelvic Nerve Crush Injury: The Possible Underlying Mechanism

PURPOSE

To explore the effect of intravesical electrical stimulation (IVES) on urinary adenosine triphosphate (ATP) and nitric oxide (NO) in rats with detrusor underactivity (DU) induced by bilateral pelvic nerve crush (bPNC), and to determine the underlying peripheral mechanism.

METHODS

Twenty-four female Sprague-Dawley rats were equally divided into 3 groups: sham; bPNC; and IVES. Rats in the IVES group began to receive IVES treatment 10 days after bPNC (20 minutes per day for 14 consecutive days). After the 14th IVES, rat urine was collected and cystometry was performed. The serum creatinine, blood urea nitrogen, and urinary ATP and NO levels were measured, and a routine urinalysis was performed.

RESULTS

The maximum cystometric capacity (MCC), maximum changes in bladder pressure during filling (∆FP), and postvoid residual urine (PVR) in the IVES group were significantly lower than the bPNC group, and the maximum changes in bladder pressure during voiding (∆VP) was significantly higher than the bPNC group. Compared with the sham group, the MCC, ∆FP and PVR were significantly increased, and the maximum voiding pressure (MVP) and ∆VP were significantly decreased in the bPNC group. After bPNC, urinary ATP was significantly decreased, and urinary NO was significantly increased. In IVES-treated rats, urinary ATP was significantly higher than the bPNC group, and NO was significantly lower than the bPNC group. In addition, the ATP-to-NO ratio of the rats in the bPNC group was significantly lower than the sham and IVES groups. Correlation analysis showed that the ATP and NO were not correlated with the MCC, ∆FP, MVP, ∆VP, and PVR.

CONCLUSION

Promoting the release of urothelial ATP and inhibiting the release of urothelial NO may be one of the peripheral mechanisms underlying IVES in the treatment of DU. Specifically, IVES may shift the balance between excitation and inhibition toward excitation.

Transient receptor potential vanilloid type 4 (TRPV4) in urinary bladder structure and function

Bladder pain syndrome (BPS)/interstitial cystitis (IC) is a urologic, chronic pelvic pain syndrome characterized by pelvic pain, pressure, or discomfort with urinary symptoms. Symptom exacerbation (flare) is common with multiple, perceived triggers including stress. Multiple transient receptor potential (TRP) channels (TRPA1, TRPV1, TRPV4) expressed in the bladder have specific tissue distributions in the lower urinary tract (LUT) and are implicated in bladder disorders including overactive bladder (OAB) and BPS/IC. TRPV4 channels are strong candidates for mechanosensors in the urinary bladder and TRPV4 antagonists are promising therapeutic agents for OAB. In this perspective piece, we address the current knowledge of TRPV4 distribution and function in the LUT and its plasticity with injury or disease with an emphasis on BPS/IC. We review our studies that extend the knowledge of TRPV4 in urinary bladder function by focusing on (i) TRPV4 involvement in voiding dysfunction, pelvic pain, and non-voiding bladder contractions in NGF-OE mice; (ii) distention-induced luminal ATP release mechanisms and (iii) involvement of TRPV4 and vesicular release mechanisms. Finally, we review our lamina propria studies in postnatal rat studies that demonstrate: (i) the predominance of the TRPV4+ and PDGFRα+ lamina propria cellular network in early postnatal rats; (ii) the ability of exogenous mediators (i.e., ATP, TRPV4 agonist) to activate and increase the number of lamina propria cells exhibiting active Ca2+ events; and (iii) the ability of ATP and TRPV4 agonist to increase the rate of integrated Ca2+ activity corresponding to coupled lamina propria network events and the formation of propagating wavefronts.

Protective Effect of Purinergic P2X7 Receptor Inhibition on Acrolein-Induced Urothelial Cell Damage

Patients undergoing chemotherapy with cyclophosphamide experience cystitis due to excretion of a toxic metabolite, acrolein. Cystitis, an inflammation of the bladder, is associated with damage to the integrity of the urothelial barrier. The purinergic P2X7 receptor (P2X7R) is increasingly recognized for its role in inflammation and cell death. P2X7R is expressed abundantly on the bladder urothelium. The aim of this study was to investigate the role of P2X7R in acrolein-induced inflammatory damage in primary cultured porcine bladder urothelial cells. Confluent urothelial cells in culture were treated with acrolein to induce damage; also, with the P2X7R selective antagonist, A804598. Cell viability assay, immunocytochemistry, and trans-epithelial electrical resistance (TEER) studies were carried out to investigate the effect of treatments on urothelial cell function. Acrolein induced a significant reduction in urothelial cell viability, which was protected by the presence of A804598 (10 µM). The urothelial barrier function, indicated by TEER values, was also significantly reduced by acrolein, whereas pre-incubation with P2X7R antagonist significantly protected the urothelial cell barrier from acrolein-induced TEER reduction. The structure of urothelial cell tight junctions was similarly impacted by acrolein treatment, showing the fragmentation of zona occludens-1 (ZO-1) immunoreactivity. Pre-treatment of cells with A804598 countered against the actions of acrolein and maintained ZO-1 expression level and cell structure. The damaging effect of acrolein on urothelial cells integrity could be impaired by inhibition of P2X7R, therefore P2X7R blockade may be a possible therapy in patients with bladder cystitis caused by cyclophosphamide treatment.

Role of detrusor PDGFRα+ cells in mouse model of cyclophosphamide-induced detrusor overactivity

Cyclophosphamide (CYP)-induced cystitis is a rodent model that shares many features common to the cystitis occurring in patients, including detrusor overactivity (DO). Platelet-derived growth factor receptor alpha positive (PDGFRα⁺) cells have been proposed to regulate muscle excitability in murine bladders during filling. PDGFRα⁺ cells express small conductance Ca²⁺-activated K⁺ channels (predominantly SK3) that provide stabilization of membrane potential during filling. We hypothesized that down-regulation of the regulatory functions of PDGFRα⁺ cells and/or loss of PDGFRα⁺ cells generates the DO in CYP-treated mice. After CYP treatment, transcripts of Pdgfrα and Kcnn3 and PDGFRα and SK3 protein were reduced in detrusor muscle extracts. The distribution of PDGFRα⁺ cells was also reduced. Inflammatory markers were increased in CYP-treated detrusor muscles. An SK channel agonist, CyPPA, increased outward current and hyperpolarization in PDGFRα⁺ cells. This response was significantly depressed in PDGFRα⁺ cells from CYP-treated bladders. Contractile experiments and ex vivo cystometry showed increased spontaneous contractions and transient contractions, respectively in CYP-treated bladders with a reduction of apamin sensitivity, that could be attributable to the reduction in the SK conductance expressed by PDGFRα⁺ cells. In summary, PDGFRα⁺ cells were reduced and the SK3 conductance was downregulated in CYP-treated bladders. These changes are consistent with the development of DO after CYP treatment.

BoNT/A in the Urinary Bladder-More to the Story than Silencing of Cholinergic Nerves

Botulinum neurotoxin (BoNT/A) is an FDA and NICE approved second-line treatment for overactive bladder (OAB) in patients either not responsive or intolerant to anti-cholinergic drugs. BoNT/A acts to weaken muscle contraction by blocking release of the neurotransmitter acetyl choline (ACh) at neuromuscular junctions. However, this biological activity does not easily explain all the observed effects in clinical and non-clinical studies. There are also conflicting reports of expression of the BoNT/A protein receptor, SV2, and intracellular target protein, SNAP-25, in the urothelium and bladder. This review presents the current evidence of BoNT/A’s effect on bladder sensation, potential mechanisms by which it might exert these effects and discusses recent advances in understanding the action of BoNT in bladder tissue.

Satisfaction with Detrusor OnabotulinumtoxinA Injections and Conversion to Other Bladder Management in Patients with Chronic Spinal Cord Injury

This study investigated the satisfaction with continued detrusor Botox injections for urinary incontinence and conversion to other surgical procedures and bladder management procedures for neurogenic detrusor overactivity (NDO) in patients with chronic spinal cord injury (SCI). A total of 223 patients with chronic SCI underwent detrusor Botox 200U for urodynamically confirmed NDO and urinary incontinence. After initial detrusor Botox injections, patients opted to either continue detrusor Botox injections every six to nine months and on clean intermittent catheterization (CIC), switch to other bladder management procedures, or receive surgical procedures to improve their urinary incontinence, correct emergent complications, or have better voiding conditions without CIC. Urinary incontinence improvement rates and satisfaction with bladder management were assessed and compared between different subgroups, urodynamic parameters, and bladder management procedures. Finally, a total of 154 male and 69 female patients were included, among whom 56 (25.1%), 81 (36.3%), 51 (22.9%), and 35 (15.7%) showed a marked, moderate, mild, and no reduction in urinary incontinence, respectively. However, only 48.4% of the patients continued detrusor Botox injections over the mean follow-up period of seven years. Patients with cervical or thoracic SCI had fair incontinence improvement rates. The presence of high detrusor pressure and higher-grade bladder outlet resistance also predicted a decrease in incontinence. Although more than 50% of the patients switched to other bladder management procedures or received surgical treatment, 69.1% expressed satisfaction with their current status. This large cohort of patients with chronic SCI who received initial detrusor Botox injections revealed that only 48.4% continued with Botox injections. Those who received surgical procedures due to urological complications or demanded change in bladder management could achieve high satisfaction rates.

Urinary Biomarkers in Interstitial Cystitis/Bladder Pain Syndrome and Its Impact on Therapeutic Outcome

Interstitial cystitis/bladder pain syndrome (IC/BPS) is defined as a chronic bladder disorder with suprapubic pain (pelvic pain) and pressure and/or discomfort related to bladder filling accompanied by lower urinary tract symptoms, such as urinary frequency and urgency without urinary tract infection (UTI) lasting for at least 6 weeks. IC/BPS presents significant bladder pain and frequency urgency symptoms with unknown etiology, and it is without a widely accepted standard in diagnosis. Patients’ pathological features through cystoscopy and histologic features of bladder biopsy determine the presence or absence of Hunner lesions. IC/PBS is categorized into Hunner (ulcerative) type IC/BPS (HIC/BPS) or non-Hunner (nonulcerative) type IC/BPS (NHIC/BPS). The pathophysiology of IC/BPS is composed of multiple possible factors, such as chronic inflammation, autoimmune disorders, neurogenic hyperactivity, urothelial defects, abnormal angiogenesis, oxidative stress, and exogenous urine substances, which play a crucial role in the pathophysiology of IC/BPS. Abnormal expressions of several urine and serum specimens, including growth factor, methylhistamine, glycoprotein, chemokine and cytokines, might be useful as biomarkers for IC/BPS diagnosis. Further studies to identify the key molecules in IC/BPS will help to improve the efficacy of treatment and identify biomarkers of the disease. In this review, we discuss the potential medical therapy and assessment of therapeutic outcome with urinary biomarkers for IC/BPS.

P2X7 Receptor Blockade Protects Against Acrolein-Induced Bladder Damage: A Potential New Therapeutic Approach for the Treatment of Bladder Inflammatory Diseases

Inflammatory conditions of the urinary bladder have been shown to be associated with urothelial damage and loss of function. The purinergic P2X7 receptor has been implicated in several inflammatory conditions. The aim of this study was to investigate the role of the P2X7 receptor in acrolein-induced inflammatory damage using the porcine urinary bladder. For this purpose, an ex-vivo model of porcine urothelial damage induced by direct instillation of acrolein into the whole bladder lumen was used. To determine the role of the P2X7 receptor, the bladders were pre-incubated with a selective P2X7 receptor antagonist, A804598 (10 μM), for 1 h. The effects of the acrolein-induced urothelial damage on the bladder’s function were assessed by examining the bladder wall contractile response, structure changes, apoptosis, and oxidative stress in the bladder tissues. The acrolein treatment led to significant damage to the urothelium histology, tight junction expression, and contractile responses. Acrolein also induced apoptosis in the mucosa layer. All these acrolein-induced responses were attenuated by pre-treatment with the P2X7 receptor antagonist A804598. Acrolein also significantly induced DNA oxidation in the submucosal layer; however, the P2X7 receptor antagonism did not show any protective effect towards the acrolein-induced oxidative stress. These findings suggested that the P2X7 receptor is involved in the acrolein-induced damage to the urothelium; therefore, the P2X7 receptor antagonists may be a new therapeutic option for the treatment of bladder inflammation.

A Systematic Review of Therapeutic Approaches Used in Experimental Models of Interstitial Cystitis/Bladder Pain Syndrome

Interstitial cystitis/bladder pain syndrome (IC/BPS) is a multifactorial, chronic bladder disorder with limited therapeutic options currently available. The present review provides an extensive overview of therapeutic approaches used in in vitro, ex vivo, and in vivo experimental models of IC/BPS. Publications were identified by electronic search of three online databases. Data were extracted for study design, type of treatment, main findings, and outcome, as well as for methodological quality and the reporting of measures to avoid bias. A total of 100 full-text articles were included. The majority of identified articles evaluated therapeutic agents currently recommended to treat IC/BPS by the American Urological Association guidelines (21%) and therapeutic agents currently approved to treat other diseases (11%). More recently published articles assessed therapeutic approaches using stem cells (11%) and plant-derived agents (10%), while novel potential drug targets identified were proteinase-activated (6%) and purinergic (4%) receptors, transient receptor potential channels (3%), microRNAs (2%), and activation of the cannabinoid system (7%). Our results show that the reported methodological quality of animal studies could be substantially improved, and measures to avoid bias should be more consistently reported in order to increase the value of preclinical research in IC/BPS for potential translation to a clinical setting.

Prostate-to-bladder cross-sensitization in a model of zymosan-induced chronic pelvic pain syndrome in rats

BACKGROUND

The aim of the present study was to investigate the effects of chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) on bladder function and pathophysiology.

METHODS

To create a model for CPPS, rats were intraprostatically injected with zymosan or saline, serving as control. Metabolic cage experiments were performed 7, 14, or 21 days after zymosan injection and after 14 days in the control group. Thereafter, cystometry was performed in which simulated micturition cycles were induced by saline infusion and contractile responses to the cholinergic agonist methacholine and the purinergic agonist ATP were measured. Following cystometry, the prostate and urinary bladder were excised and assessed histopathologically for possible inflammatory changes.

RESULTS

Metabolic cage data revealed a significantly increased urinary frequency in zymosan treated rats. Likewise, the volume per micturition was significantly lower in all CPPS groups compared to controls. Cystometry showed a significant increase in the number of nonvoiding contractions, longer voiding time, and a trend towards lower compliance in CPPS rats compared to controls. Induction of CPPS led to significantly reduced cholinergic and purinergic contractile responses. Histopathological analysis demonstrated prostatic inflammation in all CPPS groups, in particular in later stage groups. Both the extent and grade of bladder inflammation were significantly higher in CPPS groups compared to controls.

CONCLUSIONS

The current findings demonstrate a potential prostate-to-bladder cross-sensitization leading to symptoms of bladder overactivity and signs of bladder inflammation. Future clinical studies are required to verify the outcomes of the current study and enable advancement of patient care.

Frontiers in the Clinical Applications of Botulinum Toxin A as Treatment for Neurogenic Lower Urinary Tract Dysfunction

Patients with neurogenic lower urinary tract dysfunction (NLUTD) experience urinary incontinence with or without difficult urination, which might promote recurrent urinary tract infection (UTI) and exacerbate upper urinary tract function. Nonetheless, appropriate bladder management has been shown to reduce urological complications and improve quality of life. In addition to pharmacological therapy and surgical intervention, botulinum toxin A (BoNT-A) has been widely utilized in NLUTD. The therapeutic efficacy of detrusor BoNT-A injections for neurogenic detrusor overactivity due to spinal cord injury (SCI), multiple sclerosis, or other central nervous system lesions, such as cerebrovascular accident, Parkinson disease, early dementia, and pediatric NLUTD due to myelomeningocele, has been well established, with repeated BoNT-A injections every 6 to 9 months being necessary to maintain its therapeutic effects. Urethral BoNT-A injection can decrease urethral sphincter resistance and facilitate efficient voiding in patients with NLUTD who wish to preserve self-voiding. Detrusor BoNT-A injection can also decrease the occurrence of autonomic dysreflexia in patients with SCI, even after failed augmentation enterocystoplasty, with additional benefits including reduced UTI episodes and preserved renal function with repeated injections. However, this treatment does have some side effects. Complete informed consent for BoNT-A injection therapy with full disclosure of its potential complications should therefore be obtained before this procedure is undertaken.

LPS-mediated release of ATP from urothelial cells occurs by lysosomal exocytosis

BACKGROUND

While numerous studies have confirmed ATP's importance in bladder physiology/pathophysiology, the literature is still conflicted regarding the mechanism of ATP release from the urothelium. Multiple mechanisms have been identified including non-vesicular release via pannexin channels as well as vesicular release via a mechanism blocked by botulinum toxin. Recently, it has been shown that lysosomes contain significant stores of ATP which can be released extracellularly in response to Toll-like receptor (TLR) stimulation.

OBJECTIVE

The goal of the current study was to determine if lysosomal exocytosis occurs in urothelial cells in response to TLR4 stimulation by its agonist, bacterial lipopolysaccharide (LPS).

MATERIALS AND METHODS

Human urothelial cells from an immortalized cell line (TRT-HU1) were treated with bacterial LPS (100 μg/ml) or the nicotinic agoinist cytisine (100 μM) and extracellular release of ATP and lysosomal acid phosphatase were measured. Pannexin-mediated ATP release and lysosomal ATP release were differentiated using Brilliant Blue FCF to inhibit pannexin channels and glycyl-l-phenylalanine-β-naphthylamide (GPN) to destroy lysosomes. The mechanisms controlling lysosomal exocytosis were examined using lysosomal pH measurements using LysoSensor dye and intracellular calcium signaling using Fura-2.

RESULTS

Stimulation of TRT-HU1 cells with LPS significantly increased ATP release, which was inhibited by GPN, but not by Brilliant Blue FCF. Conversely, stimulation with cytisine induced ATP release that was sensitive to Brilliant Blue FCF but not GPN. LPS stimulation also induced the release of the lysosomal acid phosphatases. LPS increased lysosomal pH and direct alkalization of lysosomal pH using chloroquine or bafilomycin A1 induced ATP and acid phosphatase release, indicating an important role for pH in lysosomal exocytosis. Additionally, stimulation of lysosomal transient receptor potential mucolipin 1 calcium channels evoked intracellular calcium transients as well as ATP release.

CONCLUSION

These data indicate that LPS-induced ATP release from urothelial cells is mediated by lysosomal exocytosis, a vesicular mechanism distinctly separate from non-vesicular release via pannexin channels.

Mechanism of Action of Botulinum Toxin A in Treatment of Functional Urological Disorders

Intravesical botulinum toxin (BoNT) injection is effective in reducing urgency and urinary incontinence. It temporarily inhibits the detrusor muscle contraction by blocking the release of acetylcholine (Ach) from the preganglionic and postganglionic nerves in the efferent nerves. BoNT-A also blocks ATP release from purinergic efferent nerves in the detrusor muscle. In afferent nerves, BoNT-A injection markedly reduces the urothelial ATP release and increases nitric oxide (NO) release from the urothelium. BoNT-A injection in the urethra or bladder has been developed in the past few decades as the treatment method for detrusor sphincter dyssyndergia, incontinence due to neurogenic or idiopathic detrusor overactivity, sensory disorders, including bladder hypersensitivity, overactive bladder, and interstitial cystitis/chronic pelvic pain syndrome. Although the FDA only approved BoNT-A injection treatment for neurogenic detrusor overactivity and for refractory overactive bladder, emerging clinical trials have demonstrated the benefits of BoNT-A treatment in functional urological disorders. Cautious selection of patients and urodynamic evaluation for confirmation of diagnosis are crucial to maximize the successful outcomes of BoNT-A treatment.

Can Botulinum Toxin A Play A Role In Treatment Of Chronic Pelvic Pain Syndrome In Female Patients?-Clinical and Animal Evidence

Chronic pelvic pain (CPP) is defined as chronic pain and inflammation in the pelvic organs for more than six months. There are wide ranges of clinical presentations, including pelvic pain, painful intercourse, irritable bowel syndrome, and pain during urinating. Chronic pelvic pain syndrome (CPPS) is a subdivision of CPP, and the pain syndrome may be focused within a single organ or more than one pelvic organ. As there is uncertain pathogenesis, no standard treatment is currently available for CPPS. Botulinum toxin A (BoNT-A) is a potent neurotoxin that blocks acetylcholine release to paralyze muscles. Intravesical BoNT-A injection can reduce bladder pain in patients with interstitial cystitis/bladder pain syndrome. BoNT-A injected into the pelvic floor muscles of women has also been reported to improve chronic pain syndrome. Due to the reversible effect of BoNT-A, repeated injection appears to be necessary and effective in reducing symptoms. Adverse effects of BoNT-A may worsen the preexisting conditions, including constipation, stress urinary incontinence, and fecal incontinence. This review summarizes the evidence of BoNT-A treatment for CPPS in animal studies and clinical studies regarding the therapeutic effects of BoNT-A for CPPS in female patients.

Purinergic receptor mediated calcium signalling in urothelial cells

Non-neuronal ATP released from the urothelium in response to bladder stretch is a key modulator of bladder mechanosensation. Whilst non-neuronal ATP acts on the underlying bladder afferent nerves to facilitate sensation, there is also the potential for ATP to act in an autocrine manner, modulating urothelial cell function. The aim of this study was to systematically characterise the functional response of primary mouse urothelial cells (PMUCs) to ATP. PMUCs isolated from male mice (14–16 weeks) were used for live-cell fluorescent calcium imaging and qRT-PCR to determine the expression profile of P2X and P2Y receptors. The majority of PMUCs (74–92%) responded to ATP (1 μM–1 mM), as indicted by an increase in intracellular calcium (iCa²⁺). PMUCs exhibited dose-dependent responses to ATP (10 nM–1 mM) in both calcium containing (2 mM, EC₅₀ = 3.49 ± 0.77 μM) or calcium free (0 mM, EC₅₀ = 9.5 ± 1.5 μM) buffers. However, maximum iCa²⁺ responses to ATP were significantly attenuated upon repetitive applications in calcium containing but not in calcium free buffer. qRT-PCR revealed expression of P2X_1–6, and P2Y_1–2, P2Y₄, P2Y₆, P2Y_11–14, but not P2X₇ in PMUCs. These findings suggest the major component of ATP induced increases in iCa²⁺ are mediated via the liberation of calcium from intracellular stores, implicating functional P2Y receptors that are ubiquitously expressed on PMUCs.

The Botulinum Treatment of Neurogenic Detrusor Overactivity: The Double-Face of the Neurotoxin

Botulinum neurotoxin (BoNT) can counteract the highly frequent involuntary muscle contractions and the uncontrolled micturition events that characterize the neurogenic detrusor overactivity (NDO) due to supra-sacral spinal cord lesions. The ability of the toxin to block the neurotransmitter vesicular release causes the reduction of contractions and improves the compliance of the muscle and the bladder filling. BoNT is the second-choice treatment for NDO once the anti-muscarinic drugs have lost their effects. However, the toxin shows a time-dependent efficacy reduction up to a complete loss of activity. The cellular mechanisms responsible for BoNT effects exhaustion are not yet completely defined. Similarly, also the sites of its action are still under identification. A growing amount of data suggest that BoNT, beyond the effects on the efferent terminals, would act on the sensory system recently described in the bladder mucosa. The specimens from NDO patients no longer responding to BoNT treatment displayed a significant increase of the afferent terminals, likely excitatory, and signs of a chronic neurogenic inflammation in the mucosa. In summary, beyond the undoubted benefits in ameliorating the NDO symptomatology, BoNT treatment might bring to alterations in the bladder sensory system able to shorten its own effectiveness.

TRPV4 blockade reduces voiding frequency, ATP release, and pelvic sensitivity in mice with chronic urothelial overexpression of NGF

Transient receptor potential vanilloid family member 4 (TRPV4) transcript and protein expression increased in the urinary bladder and lumbosacral dorsal root ganglia of transgenic mice with chronic urothelial overexpression of nerve growth factor (NGF-OE). We evaluated the functional role of TRPV4 in bladder function with open-outlet cystometry, void spot assays, and natural voiding (Urovoid) assays with the TRPV4 antagonist HC-067047 (1 μM) or vehicle in NGF-OE and littermate wild-type (WT) mice. Blockade of TRPV4 at the level of the urinary bladder significantly (P ≤ 0.01) increased the intercontraction interval (2.2-fold) and void volume (2.6-fold) and decreased nonvoiding contractions (3.0-fold) in NGF-OE mice, with lesser effects (1.3-fold increase in the intercontraction interval and 1.3-fold increase in the void volume) in WT mice. Similar effects of TRPV4 blockade on bladder function in NGF-OE mice were demonstrated with natural voiding assays. Intravesical administration of HC-067047 (1 µM) significantly (P ≤ 0.01) reduced pelvic sensitivity in NGF-OE mice but was without effect in littermate WT mice. Blockade of urinary bladder TRPV4 or intravesical infusion of brefeldin A significantly (P ≤ 0.01) reduced (2-fold) luminal ATP release from the urinary bladder in NGF-OE and littermate WT mice. The results of the present study suggest that TRPV4 contributes to luminal ATP release from the urinary bladder and increased voiding frequency and pelvic sensitivity in NGF-OE mice.

Purinergic P2X7 receptors as therapeutic targets in interstitial cystitis/bladder pain syndrome; key role of ATP signaling in inflammation

Interstitial cystitis/bladder pain syndrome (IC/BPS) is a chronic lower urinary tract condition. Patients with IC/BPS suffer from debilitating pain and urinary urgency. The underlying etiology of IC/BPS is unknown and as such current treatments are mostly symptomatic with no real cure. Many theories have been proposed to describe the etiology of IC/BPS, but this review focuses on the role of inflammation. In IC/BPS patients, the permeability of the urothelium barrier is compromised and inflammatory cells infiltrate the bladder wall. There are increased levels of many inflammatory mediators in patients with IC/BPS and symptoms such as pain and urgency that have been associated with the degree of inflammation. Recent evidence has highlighted the role of purinergic receptors, specifically the P2X7 receptor, in the process of inflammation. The results from studies in animals including cyclophosphamide-induced hemorrhagic cystitis strongly support the role of P2X7 receptors in inflammation. Furthermore, the deletion of the P2X7 receptor or antagonism of this receptor significantly reduces inflammatory mediator release from the bladder and improves symptoms. Research results from IC/BPS patients and animal models of IC/BPS strongly support the crucial role of inflammation in the pathophysiology of this painful disease. Purinergic signaling and purinergic receptors, especially the P2X7 receptor, play an undisputed role in inflammation. Purinergic receptor antagonists show positive results in treating different symptoms of IC/BPS.

Mechanisms Underlying Overactive Bladder and Interstitial Cystitis/Painful Bladder Syndrome

The bladder is innervated by extrinsic afferents that project into the dorsal horn of the spinal cord, providing sensory input to the micturition centers within the central nervous system. Under normal conditions, the continuous activation of these neurons during bladder distension goes mostly unnoticed. However, for patients with chronic urological disorders such as overactive bladder syndrome (OAB) and interstitial cystitis/painful bladder syndrome (IC/PBS), exaggerated bladder sensation and altered bladder function are common debilitating symptoms. Whilst considered to be separate pathological entities, there is now significant clinical and pre-clinical evidence that both OAB and IC/PBS are related to structural, synaptic, or intrinsic changes in the complex signaling pathways that mediate bladder sensation. This review discusses how urothelial dysfunction, bladder permeability, inflammation, and cross-organ sensitisation between visceral organs can regulate this neuroplasticity. Furthermore, we discuss how the emotional affective component of pain processing, involving dysregulation of the HPA axis and maladaptation to stress, anxiety and depression, can exacerbate aberrant bladder sensation and urological dysfunction. This review reveals the complex nature of urological disorders, highlighting numerous interconnected mechanisms in their pathogenesis. To find appropriate therapeutic treatments for these disorders, it is first essential to understand the mechanisms responsible, incorporating research from every level of the sensory pathway, from bladder to brain.

I-Tiao-Gung extract through its active component daidzin improves cyclophosphamide-induced bladder dysfunction in rat model

AIMS

We explored the therapeutic potential of intragastric administration traditional Chinese medicine Glycine tomentella Hayata (I-Tiao-Gung, ITG) extract and its active component Daidzin on cyclophosphamide (CYP)-induced cystitis and bladder hyperactivity in rats.

METHODS

Female Wistar rats were divided into control, CYP (200 mg/kg), CYP + ITG (1.17 g/kg/day), CYP + Daidzin (12.5 mg/kg/day), and 1 week of ITG preconditioning with CYP (ITG + CYP) groups. We determined the trans cystometrogram associated with external urethral sphincter electromyogram, and the expression of M2 and M3 muscarinic and P2 × 2 and P2 × 3 purinergic receptors by Western blot in these animals.

RESULTS

ITG extract contains 1.07% of Daidzin and 0.77% of Daidzein by high-performance liquid chromatography. Daidzin was more efficient than Daidzein in scavenging H₂ O₂ activity by a chemiluminescence analyzer. CYP induced higher frequency, shorter intercontraction interval, lower maximal voiding pressure, lower threshold pressure, and Phase-2 emptying contraction with a depressed external urethral sphincter electromyogram activity, and hemorrhagic cystitis in the bladders. The altered parameters by CYP were significantly improved in CYP + ITG, CYP + Daidzin, and ITG + CYP groups. The P2 × 2 and P2 × 3 expressions were significantly upregulated in CYP group, but were depressed in CYP + ITG, CYP + Daidzin, and ITG + CYP groups. The M2 expression was not significantly different among these five groups. The M3 expression was significantly upregulated in CYP group, but was significantly depressed in CYP + ITG, CYP + Daidzin, and ITG + CYP groups.

CONCLUSIONS

These data suggest that ITG extract through its active component Daidzin effectively improved CYP-induced cystitis by the action of restoring Phase 2 activity and inhibiting the expressions of P2 × 2, P2 × 3, and M3 receptors.

Therapeutic use of botulinum toxin in pain treatment

Botulinum toxin is one of the most potent molecule known to mankind. A neurotoxin, with high affinity for cholinergic synapse, is effectively capable of inhibiting the release of acetylcholine. On the other hand, botulinum toxin is therapeutically used for several musculoskeletal disorders. Although most of the therapeutic effect of botulinum toxin is due to temporary skeletal muscle relaxation (mainly due to inhibition of the acetylcholine release), other effects on the nervous system are also investigated. One of the therapeutically investigated areas of the botulinum neurotoxin (BoNT) is the treatment of pain. At present, it is used for several chronic pain diseases, such as myofascial syndrome, headaches, arthritis, and neuropathic pain. Although the effect of botulinum toxin in pain is mainly due to its effect on cholinergic transmission in the somatic and autonomic nervous systems, research suggests that botulinum toxin can also provide benefits related to effects on cholinergic control of cholinergic nociceptive and antinociceptive systems. Furthermore, evidence suggests that botulinum toxin can also affect central nervous system (CNS). In summary, botulinum toxin holds great potential for pain treatments. It may be also useful for the pain treatments where other methods are ineffective with no side effect(s). Further studies will establish the exact analgesic mechanisms, efficacy, and complication of botulinum toxin in chronic pain disorders, and to some extent acute pain disorders.

Diabetes-induced alterations in urothelium function: Enhanced ATP release and nerve-evoked contractions in the streptozotocin rat bladder

Up to 80% of patients with diabetes mellitus develop lower urinary tract complications, most commonly diabetic bladder dysfunction (DBD). The aim of this study was to investigate the impact of diabetes on the function of the inner bladder lining (urothelium). Bladder compliance and intraluminal release of urothelial mediators, adenosine triphosphate (ATP) and acetylcholine (ACh) in response to distension were investigated in whole bladders isolated from 2- and 12-week streptozotocin (STZ)-diabetic rats. Intact and urothelium-denuded bladder strips were used to assess the influence of the urothelium on bladder contractility. Intraluminal ATP release was significantly enhanced at 2 weeks of diabetes, although not at 12 weeks. In contrast, intraluminal ACh release was unaltered by diabetes. Bladder compliance was also significantly enhanced at both 2 and 12 weeks of diabetes, with greatly reduced intravesical pressures in response to distension. Nerve-evoked contractions of bladder strips were significantly greater at 2 weeks of diabetes. When the urothelium was absent, nerve-evoked contractions were reduced, but contractions remained significantly elevated at lower frequencies of stimulation (<5 Hz) in diabetics. Interestingly, although relaxations of bladder strips to isoprenaline were unaltered by diabetes, removal of the urothelium unmasked significantly enhanced relaxations in strips from 2- and 12-week diabetic animals. In conclusion, diabetes alters urothelial function. Enhanced urothelial ATP release may be involved in the hypercontractility observed at early time points of diabetes. These alterations are time-dependent and may contribute to the mechanisms at play during the development of diabetic bladder dysfunction.

Role of neurogenic inflammation in local communication in the visceral mucosa

Intense research has focused on the involvement of the nervous system in regard to cellular mechanisms underlying neurogenic inflammation in the pelvic viscera. Evidence supports the neural release of inflammatory factors, trophic factors, and neuropeptides in the initiation of inflammation. However, more recently, non-neuronal cells including epithelia, endothelial, mast cells, and paraneurons are likely important participants in nervous system functions. For example, the urinary bladder urothelial cells are emerging as key elements in the detection and transmission of both physiological and nociceptive stimuli in the lower urinary tract. There is mounting evidence that these cells are involved in sensory mechanisms and can release mediators. Further, localization of afferent nerves next to the urothelium suggests these cells may be targets for transmitters released from bladder nerves and that chemicals released by urothelial cells may alter afferent excitability. Modifications of this type of communication in a number of pathological conditions can result in altered release of epithelial-derived mediators, which can activate local sensory nerves. Taken together, these and other findings highlighted in this review suggest that neurogenic inflammation involves complex anatomical and physiological interactions among a number of cell types in the bladder wall. The specific factors and pathways that mediate inflammatory responses in both acute and chronic conditions are not well understood and need to be further examined. Elucidation of mechanisms impacting on these pathways may provide insights into the pathology of various types of disorders involving the pelvic viscera.

Single onabotulinumtoxinA 200U dose improved clinical symptoms but not urothelial dysfunction in neurogenic detrusor overactivity due to spinal cord injury

OBJECTIVE

To evaluate the changes in urothelial dysfunction protein expressions in bladder after onabotulinumtoxin injection and correlate that with clinical outcomes in spinal cord injury (SCI) patients.

METHODS

Twenty-six patients with neurogenic detrusor overactivity (NDO) and urinary incontinence due to suprasacral SCI were treated with onabotulinumtoxinA 200U detrusor injection. Urodynamic studies and bladder biopsies were obtained at baseline, 3, and 6 months after treatment. Biopsy tissues were investigated for E-cadherin, zonula occludens-1 (ZO-1), mast cell activity, and urothelial cell apoptosis, sensory protein expression including purinergic receptor P2X3, endothelial NOS, inducible NOS, β3-adrenoceptors, and muscarinic receptors M2 and M3. Differences in functional protein expression between controls and SCI patients and between successful and failed treatment groups were analyzed.

RESULTS

SCI patients had significantly lower E-cadherin, higher mast cell activity, increased apoptosis, decreased M3 and eNOS expressions than the controls at baseline. Of the 26 patients, 17 (65%) showed improvement in bladder capacity by >50% at 3 months; however, improvement declined by 6 months after treatment. The urothelial expression of E-cadherin and ZO-1 increased at 3 months but had declined at 6 months. The urothelial sensory protein expression did not change significantly after treatment. M3 receptor density was significantly decreased in SCI patients at baseline and patients with treatment success 3 months after injection (p = 0.01).

CONCLUSION

A single injection of onabotulinumtoxinA 200U improved clinical symptoms but did not significantly alter urothelial sensory protein expression. The results imply that a single 200U onabotulinumtoxinA dose might not be adequate for urothelial dysfunction in NDO. IRB: TCGH 098-53.

The efficacy of botulinum toxin A and sacral neuromodulation in the management of interstitial cystitis (IC)/bladder pain syndrome (BPS), what do we know? ICI-RS 2017 think thank, Bristol

AIMS

This manuscript aims to address the evidence availale in the literature on the efficacy of Botulinum Toxin A (BoNT-A) and sacral neuromodulation (SNM) in patients suffering from Interstitial Cystitis (IC)/BPS and propose further research to identify mechanisms of action and establish the clinical efficacy of either therapy.

METHODS

At the International Consultation on Incontinence-Research Society (ICI-RS) in 2017, a panel of Functional Urologists and Urogynaecologists participated in a Think Tank (TT) discussing the management of IC/BPS by BoNT-A and SNM, using available data from both PubMed and Medicine literature searches.

RESULTS

The role of BoNT-A and SNM in the treatment of IC/BPS are discussed and mechanisms of actions are proposed. Despite the available randomized trial data on the effect of intravesical BoNT-A treatment on symptoms of IC/BPS, a consistent conclusion of a positive effect cannot be drawn at the moment, as the published studies are small and heterogeneous in design. There is substantive evidence for the positive effects of SNM on symptoms of IC/BPS patients however, during patient selection, it is important to distinguish the degree and the location of pain in order to tailor the best therapy to the right patients.

CONCLUSIONS

Both intravesical BoNT-A treatment and SNM have been shown to have positive effects in patients with IC/BPS. However, firm conclusions cannot yet be drawn. Patient-reported outcomes and quality of life should be assessed in addition to urinary and pain symptoms. Since current treatments mainly focus on symptomatic relief, future research should also focus on clarifying the pathogenic mechanisms involved in IC/BPS.

Safety and Feasibility of Intravesical Instillation of Botulinum Toxin-A in Hydrogel-based Slow-release Delivery System in Patients With Interstitial Cystitis-Bladder Pain Syndrome: A Pilot Study

OBJECTIVE

To assess the feasibility and the safety of a mixture instillation of TC-3 gel, a novel reverse-thermal gelation hydrogel, and botulinum toxin-A (BTX-A) for the treatment of interstitial cystitis-bladder pain syndrome (IC/BPS). TC-3 gel-BTX-A mix is instilled into the bladder as liquid, solidifies because of body heat, and gradually dissolves to release BTX-A for several hours.

METHODS

A single intravesical instillation of 200 U BTX-A premixed with 40 mL TC-3 gel was delivered to the bladder. Adverse events and preliminary efficacy outcome measures were assessed: bladder diary, visual analog scale (VAS) for pain, and Interstitial Cystitis Symptom Index (ICSI) and Interstitial Cystitis Problem Index (ICPI) at baseline and at 2, 6, and 12 weeks.

RESULTS

A total of 15 severely symptomatic patients with IC/BPS (ICSI and ICPI score ranges 12-19 and 12-16, respectively; median VAS = 7) were enrolled (male and female = 4 and 11, ages 24-76). In terms of safety, no increase in VAS score was noted at instillation. All adverse events were transient and mild, the most common being temporary mild constipation (n = 4, 26%). The mean VAS at baseline vs week 12 was 6.6 ± 2.7 vs 5.3 ± 2.8 (P = .044). The mean ICSI and ICPI scores were reduced at week 12 compared with baseline (15.4 ± 2.4 vs 12.9 ± 4.3, P = .004, and 14.8 ± 1.4 vs 11.9 ± 4.0, P = .004, respectively). The mean number of voids per night at baseline decreased for 6 weeks (3.3 ± 2.1 vs 1.8 ± 0.9, P = .046) and then returned to baseline level at week 12.

CONCLUSION

Intravesical instillation of a TC-3 gel-BTX-A mixture is safe and tolerable. Preliminary results suggest temporary efficacy lasting for a few weeks.

Purinergic Signalling: Therapeutic Developments

Purinergic signalling, i.e., the role of nucleotides as extracellular signalling molecules, was proposed in 1972. However, this concept was not well accepted until the early 1990's when receptor subtypes for purines and pyrimidines were cloned and characterised, which includes four subtypes of the P1 (adenosine) receptor, seven subtypes of P2X ion channel receptors and 8 subtypes of the P2Y G protein-coupled receptor. Early studies were largely concerned with the physiology, pharmacology and biochemistry of purinergic signalling. More recently, the focus has been on the pathophysiology and therapeutic potential. There was early recognition of the use of P1 receptor agonists for the treatment of supraventricular tachycardia and A2A receptor antagonists are promising for the treatment of Parkinson's disease. Clopidogrel, a P2Y12 antagonist, is widely used for the treatment of thrombosis and stroke, blocking P2Y12 receptor-mediated platelet aggregation. Diquafosol, a long acting P2Y2 receptor agonist, is being used for the treatment of dry eye. P2X3 receptor antagonists have been developed that are orally bioavailable and stable in vivo and are currently in clinical trials for the treatment of chronic cough, bladder incontinence, visceral pain and hypertension. Antagonists to P2X7 receptors are being investigated for the treatment of inflammatory disorders, including neurodegenerative diseases. Other investigations are in progress for the use of purinergic agents for the treatment of osteoporosis, myocardial infarction, irritable bowel syndrome, epilepsy, atherosclerosis, depression, autism, diabetes, and cancer.

Protocol for a prospective observational study of cortical lower urinary tract control changes following intradetrusor injection of botulinum toxin-A in patients with multiple sclerosis

INTRODUCTION

Multiple sclerosis (MS) is a severe debilitating disease that affects patients' quality of life. Up to 90% of patients with MS will develop lower urinary tract dysfunction within the first 18 years of the disease. If oral pharmacotherapy with anticholinergics, behavioural modifications and pelvic floor physical therapy are unsuccessful, intradetrusor injection of botulinum toxin-A (OnaBotA; Botox Allergan, Dublin, Ireland) is a highly effective option for these patients. The local effects of OnaBotA are well understood, but not much is known of its afferent/sensory effects while treating the end organ. Our study will use functional MRI (fMRI) and task-related blood oxygen level-dependent signals to evaluate patients with MS and neurogenic detrusor overactivity (NDO) prior to, and after, intradetrusor injection of OnaBotA with simultaneous urodynamic evaluation. Urinary concentration of brain-derived neurotrophic factor and nerve growth factor will also be collected since it has been shown that patients with an overactive bladder have higher concentrations of these neuropeptides.

METHODS AND ANALYSIS

Female patients with MS and lower urinary tract symptoms who previously have undergone urodynamic screening and are refractory to conservative and oral pharmacotherapy management for NDO and are interested in OnaBotA intradetrusor injection will be invited to participate in the study. An fMRI will be performed preintradetrusor injection and postintradetrusor injection of OnaBotA with simultaneous MRI compatible with material urodynamics. Images will be collected and analysed accordingly.

ETHICS AND DISSEMINATION

All of the patients are properly consented before enrolling in this study that has been previously approved by the Institutional Review Board. Results of neural connectivity activation will be presented at national and international meetings and published in scholarly journals.

The Role of the Mucosa in Normal and Abnormal Bladder Function

The internal face of the detrusor smooth muscle wall of the urinary bladder is covered by a mucosa, separating muscle from the hostile environment of urine. However, the mucosa is more than a very low permeability structure and offers a sensory function that monitors the extent of bladder filling and composition of the urine. The mucosa may be considered as a single functional structure and comprises a tight epithelial layer under which is a basement membrane and lamina propria. The latter region itself is a complex of afferent nerves, blood vessels, interstitial cells and in some species including human beings a muscularis mucosae. Stress on the bladder wall through physical or chemical stressors elicits release of chemicals, such as ATP, acetylcholine, prostaglandins and nitric oxide that modulate the activity of either afferent nerves or the muscular components of the bladder wall. The release and responses are graded so that the mucosa forms a dynamic sensory structure, and there is evidence that the gain of this system is increased in pathologies such as overactive bladder and bladder pain syndrome. This system therefore potentially provides a number of drug targets against these conditions, once a number of fundamental questions are answered. These include how is mediator release regulated; what are the intermediate roles of interstitial cells that surround afferent nerves and blood vessels; and what is the mode of communication between urothelium and muscle - by diffusion of mediators or by cell-to-cell communication?

Urothelial ATP exocytosis: regulation of bladder compliance in the urine storage phase

The bladder urothelium is more than just a barrier. When the bladder is distended, the urothelium functions as a sensor to initiate the voiding reflex, during which it releases ATP via multiple mechanisms. However, the mechanisms underlying this ATP release in response to the various stretch stimuli caused by bladder filling remain largely unknown. Therefore, the aim of this study was to elucidate these mechanisms. By comparing vesicular nucleotide transporter (VNUT)-deficient and wild-type male mice, we showed that ATP has a crucial role in urine storage through exocytosis via a VNUT-dependent mechanism. VNUT was abundantly expressed in the bladder urothelium, and when the urothelium was weakly stimulated (i.e. in the early filling stages), it released ATP by exocytosis. VNUT-deficient mice showed reduced bladder compliance from the early storage phase and displayed frequent urination in inappropriate places without a change in voiding function. We conclude that urothelial, VNUT-dependent ATP exocytosis is involved in urine storage mechanisms that promote the relaxation of the bladder during the early stages of filling.

Characterization of muscarinic and P2X receptors in the urothelium and detrusor muscle of the rat bladder

Muscarinic and purinergic (P2X) receptors play critical roles in bladder urothelium under physiological and pathological conditions. Aim of present study was to characterize these receptors in rat bladder urothelium and detrusor muscle using selective radioligands of [N-methyl-(3)H]scopolamine methyl chloride ([(3)H]NMS) and αβ-methylene ATP [2,8-(3)H]tetrasodium salt ([(3)H]αβ-MeATP). Similar binding parameters for each radioligand were observed in urothelium and detrusor muscle. Pretreatment with N-(2-chloroethyl)-4-piperidinyl diphenylacetate (4-DAMP mustard) mustard revealed co-existence of M2 and M3 receptors, with the number of M2 receptors being larger in the urothelium and detrusor muscle. Intravesical administration of imidafenacin and Dpr-P-4 (N → O) (active metabolite of propiverine) displayed significant binding of muscarinic receptors in the urothelium and detrusor muscle. The treatment with cyclophosphamide (CYP) or resiniferatoxin (RTX) resulted in a significant decrease in maximal number of binding sites (Bmax) for [(3)H]NMS and/or [(3)H]αβ-MeATP in the urothelium and detrusor muscle. These results demonstrated that 1) pharmacological characteristics of muscarinic and P2X receptors in rat bladder urothelium were similar to those in the detrusor muscle, 2) that densities of these receptors were significantly altered by pretreatments with CYP and RTX, and 3) that these receptors may be pharmacologically affected by imidafenacin and Dpr-P-4 (N → O) which are excreted in the urine.

Purinergic signalling underlies transforming growth factor-β-mediated bladder afferent nerve hyperexcitability

KEY POINTS

The sensory components of the urinary bladder are responsible for the transduction of bladder filling and are often impaired with neurological injury or disease. Elevated extracellular ATP contributes, in part, to bladder afferent nerve hyperexcitability during urinary bladder inflammation or irritation. Transforming growth factor-β1 (TGF-β1) may stimulate ATP release from the urothelium through vesicular exocytosis mechanisms with minimal contribution from pannexin-1 channels to increase bladder afferent nerve discharge. Bladder afferent nerve hyperexcitability and urothelial ATP release with CYP-induced cystitis is decreased with TGF-β inhibition. These results establish a causal link between an inflammatory mediator, TGF-β, and intrinsic signalling mechanisms of the urothelium that may contribute to the altered sensory processing of bladder filling.

ABSTRACT

The afferent limb of the micturition reflex is often compromised following bladder injury, disease and inflammatory conditions. We have previously demonstrated that transforming growth factor-β (TGF-β) signalling contributes to increased voiding frequency and decreased bladder capacity with cystitis. Despite the functional presence of TGF-β in bladder inflammation, the precise mechanisms of TGF-β mediating bladder dysfunction are not yet known. Thus, the present studies investigated the sensory components of the urinary bladder that may underlie the pathophysiology of aberrant TGF-β activation. We utilized bladder-pelvic nerve preparations to characterize bladder afferent nerve discharge and the mechanisms of urothelial ATP release with distention. Our findings indicate that bladder afferent nerve discharge is sensitive to elevated extracellular ATP during pathological conditions of urinary bladder inflammation or irritation. We determined that TGF-β1 may increase bladder afferent nerve excitability by stimulating ATP release from the urothelium via vesicular exocytosis mechanisms with minimal contribution from pannexin-1 channels. Furthermore, blocking aberrant TGF-β signalling in cyclophosphamide-induced cystitis with TβR-1 inhibition decreased afferent nerve hyperexcitability with a concomitant decrease in urothelial ATP release. Taken together, these results establish a role for purinergic signalling mechanisms in TGF-β-mediated bladder afferent nerve activation that may ultimately facilitate increased voiding frequency. The synergy between intrinsic urinary bladder signalling mechanisms and an inflammatory mediator provides novel insight into bladder dysfunction and supports new avenues for therapeutic intervention.

Purinergic Mechanisms and Pain

There is a brief introductory summary of purinergic signaling involving ATP storage, release, and ectoenzymatic breakdown, and the current classification of receptor subtypes for purines and pyrimidines. The review then describes purinergic mechanosensory transduction involved in visceral, cutaneous, and musculoskeletal nociception and on the roles played by receptor subtypes in neuropathic and inflammatory pain. Multiple purinoceptor subtypes are involved in pain pathways both as an initiator and modulator. Activation of homomeric P2X3 receptors contributes to acute nociception and activation of heteromeric P2X2/3 receptors appears to modulate longer-lasting nociceptive sensitivity associated with nerve injury or chronic inflammation. In neuropathic pain activation of P2X4, P2X7, and P2Y12 receptors on microglia may serve to maintain nociceptive sensitivity through complex neural-glial cell interactions and antagonists to these receptors reduce neuropathic pain. Potential therapeutic approaches involving purinergic mechanisms will be discussed.

Current and potential urological applications of botulinum toxin A

Botulinum toxin subtype A (BoNT-A) is a potent neurotoxin that can selectively modulate neurotransmitter release from nerve endings, resulting in muscular paralysis. BoNT-A might also act on sensory nerves, and have an anti-inflammatory effect. In the first urological use of BoNT-A, injection into the urethral sphincters of patients with detrusor-sphincter dyssynergia resulted in a reduction of urethral resistance and improved voiding efficiency. Subsequently, intravesical BoNT-A injections have received regulatory approval for treatment of neurogenic detrusor overactivity owing to spinal cord lesions or multiple sclerosis, and idiopathic overactive bladder in adults. BoNT-A has also been widely used to treat patients with the off-label indications of neurogenic or non-neurogenic voiding dysfunction and male lower urinary tract symptoms owing to BPH and bladder-neck dysfunction. Other indications for which urologists have applied BoNT-A injections include interstitial cystitis/bladder pain syndrome, bladder oversensitivity and chronic pelvic pain syndrome. BoNT-A is currently delivered as an intravesical injection; however, use of liposome encapsulated formulations is also beginning to show some therapeutic potential.

O'Leary-Sant Symptom Index Predicts the Treatment Outcome for OnabotulinumtoxinA Injections for Refractory Interstitial Cystitis/Bladder Pain Syndrome

Although intravesical injection of onabotulinumtoxinA (BoNT-A) has been proved promising in treating patients with interstitial cystitis/bladder pain syndrome (IC/BPS), what kind of patients that may benefit from this treatment remains unclear. This study investigated the predictors for a successful treatment outcome. Patients with IC/BPS who failed conventional treatments were enrolled to receive intravesical injection of 100 U of BoNT-A immediately followed by hydrodistention. Variables such as O’Leary-Sant symptom and problem indexes (ICSI and ICPI), pain visual analogue scale (VAS), functional bladder capacity (FBC), voiding diary, and urodynamic parameters were measured at baseline and six months after treatment. A global response assessment (GRA) ≥ 2 at six months was defined as successful. There were101 patients enrolled. Significant improvements were observed in mean ICSI, ICPI, OSS (ICSI + ICPI), pain VAS, FBC, frequency, nocturia and GRA at six months after BoNT-A injections (all p < 0.05). The successful rate at six months was 46/101 (45.54%). Multivariate logistic regression revealed the baseline ICSI (odds ratio = 0.770, 95% confidence interval = 0.601–0.989) was the only predictor for a treatment outcome. ICSI ≥ 12 was the most predictive cutoff value for a treatment failure, with a ROC area of 0.70 (sensitivity = 69.1%, specificity = 60.9%).

The effects of tempol on cyclophosphamide-induced oxidative stress in rat micturition reflexes

We hypothesized that cyclophosphamide- (CYP-) induced cystitis results in oxidative stress and contributes to urinary bladder dysfunction. We determined (1) the expression of oxidative stress markers 3-nitrotyrosine (3-NT), reactive oxygen species (ROS)/reactive nitrogen species (RNS), inflammatory modulators, neuropeptides calcitonin gene-related peptide (CGRP), substance P (Sub P), and adenosine triphosphate (ATP) that contribute to the inflammatory process in the urinary tract and (2) the functional role of oxidative stress in urinary bladder dysfunction with an antioxidant, Tempol, (1 mM in drinking water) combined with conscious cystometry. In CYP-treated (4 hr or 48 hr; 150 mg/kg, i.p.) rats, ROS/RNS and 3-NT significantly (P ≤ 0.01) increased in urinary bladder. CYP treatment increased ATP, Sub P, and CGRP expression in the urinary bladder and cystometric fluid. In CYP-treated rats, Tempol significantly (P ≤ 0.01) increased bladder capacity and reduced voiding frequency compared to CYP-treated rats without Tempol. Tempol significantly (P ≤ 0.01) reduced ATP expression, 3-NT, and ROS/RNS expression in the urinary tract of CYP-treated rats. These studies demonstrate that reducing oxidative stress in CYP-induced cystitis improves urinary bladder function and reduces markers of oxidative stress and inflammation.

Pannexin 1 channels mediate the release of ATP into the lumen of the rat urinary bladder

KEY POINTS

ATP is released through pannexin channels into the lumen of the rat urinary bladder in response to distension or stimulation with bacterial endotoxins. Luminal ATP plays a physiological role in the control of micturition because intravesical perfusion of apyrase or the ecto-ATPase inhibitor ARL67156 altered reflex bladder activity in the anaesthetized rat. The release of ATP from the apical and basolateral surfaces of the urothelium appears to be mediated by separate mechanisms because intravesical administration of the pannexin channel antagonist Brilliant Blue FCF increased bladder capacity, whereas i.v. administration did not. Intravesical instillation of small interfering RNA-containing liposomes decreased pannexin 1 expression in the rat urothelium in vivo and increased bladder capacity. These data indicate a role for pannexin-mediated luminal ATP release in both the physiological and pathophysiological control of micturition and suggest that urothelial pannexin may be a viable target for the treatment of overactive bladder disorders.

ABSTRACT

ATP is released from the bladder epithelium, also termed the urothelium, in response to mechanical or chemical stimuli. Although numerous studies have described the contribution of this release to the development of various bladder disorders, little information exists regarding the mechanisms of release. In the present study, we examined the role of pannexin channels in mechanically-induced ATP release from the urothelium. PCR confirmed the presence of pannexin 1 and 2 mRNA in rat urothelial tissue, whereas immunofluorescence experiments localized pannexin 1 to all three layers of the urothelium. During continuous bladder cystometry in anaesthetized rats, inhibition of pannexin 1 channels using carbenoxolone (CBX) or Brilliant Blue FCF (BB-FCF) (1-100 μm, intravesically), or by using intravesical small interfering RNA, increased the interval between voiding contractions. Intravenous administration of BB-FCF (1-100 μg kg(-1) ) did not alter bladder activity. CBX or BB-FCF (100 μm intravesically) also decreased basal ATP concentrations in the perfusate from non-distended bladders and inhibited increases in ATP concentrations in response to bladder distension (15 and 30 cmH2 O pressure). Intravesical perfusion of the ATP diphosphohydrolase apyrase (2 U ml(-1) ), or the ATPase inhibitor ARL67156 (10 μm) increased or decreased reflex bladder activity, respectively. Intravesical instillation of bacterial lipopolysaccharides (LPS) (Escherichia coli 055:B5, 100 μg ml(-1) ) increased ATP concentrations in the bladder perfusate, and also increased voiding frequency; these effects were suppressed by BB-FCF. These data indicate that pannexin channels contribute to distension- or LPS-evoked ATP release into the lumen of the bladder and that luminal release can modulate voiding function.

Pannexin 1 channels play essential roles in urothelial mechanotransduction and intercellular signaling

Urothelial cells respond to bladder distension with ATP release, and ATP signaling within the bladder and from the bladder to the CNS is essential for proper bladder function. In other cell types, pannexin 1 (Panx1) channels provide a pathway for mechanically-induced ATP efflux and for ATP-induced ATP release through interaction with P2X₇ receptors (P2X₇Rs). We report that Panx1 and P2X₇R are functionally expressed in the bladder mucosa and in immortalized human urothelial cells (TRT-HU1), and participate in urothelial ATP release and signaling. ATP release from isolated rat bladders induced by distention was reduced by the Panx1 channel blocker mefloquine (MFQ) and was blunted in mice lacking Panx1 or P2X₇R expression. Hypoosmotic shock induced YoPro dye uptake was inhibited by MFQ and the P2X₇R blocker A438079 in TRT-HU1 cells, and was also blunted in primary urothelial cells derived from mice lacking Panx1 or P2X₇R expression. Rinsing-induced mechanical stimulation of TRT-HU1 cells triggered ATP release, which was reduced by MFQ and potentiated in low divalent cation solution (LDPBS), a condition known to enhance P2X₇R activation. ATP signaling evaluated as intercellular Ca²⁺ wave radius was significantly larger in LDPBS, reduced by MFQ and by apyrase (ATP scavenger). These findings indicate that Panx1 participates in urothelial mechanotransduction and signaling by providing a direct pathway for mechanically-induced ATP release and by functionally interacting with P2X₇Rs.

Local receptors as novel regulators for peripheral clock expression

Mammalian circadian control is determined by a central clock in the brain suprachiasmatic nucleus (SCN) and synchronized peripheral clocks in other tissues. Increasing evidence suggests that SCN-independent regulation of peripheral clocks also occurs. We examined how activation of excitatory receptors influences the clock protein PERIOD 2 (PER2) in a contractile organ, the urinary bladder. PERIOD2::LUCIFERASE-knock-in mice were used to report real-time PER2 circadian dynamics in the bladder tissue. Rhythmic PER2 activities occurred in the bladder wall with a cycle of ∼24 h and peak at ∼12 h. Activation of the muscarinic and purinergic receptors by agonists shifted the peak to an earlier time (7.2±2.0 and 7.2±0.9 h, respectively). PER2 expression was also sensitive to mechanical stimulation. Aging significantly dampened PER2 expression and its response to the agonists. Finally, muscarinic agonist-induced smooth muscle contraction also exhibited circadian rhythm. These data identified novel regulators, endogenous receptors, in determining local clock activity, in addition to mediating the central control. Furthermore, the local clock appears to reciprocally align receptor activity to circadian rhythm for muscle contraction. The interaction between receptors and peripheral clock represents an important mechanism for maintaining physiological functions and its dysregulation may contribute to age-related organ disorders.—Wu, C., Sui, G., Archer, S. N., Sassone-Corsi, P., Aitken, K., Bagli, D., Chen, Y. Local receptors as novel regulators for peripheral clock expression.