Immunohistochemical expression of muscarinic receptors in the urothelium and suburothelium of neurogenic and idiopathic overactive human bladders, and changes with botulinum neurotoxin administration

Onabotulinum toxin A improves neurogenic detrusor overactivity following spinal cord injury: a systematic review and meta-analysis

STUDY DESIGN

Systematic review and meta-analysis.

OBJECTIVES

The current study aimed to assess the efficacy and safety of Onabotulinum toxin A (OBTX-A) treatment for neurogenic detrusor overactivity (NDO) in spinal cord injury (SCI) patients.

SETTING

Iran.

METHODS

All relevant articles of clinical trials and cohort studies indexed in PubMed/MEDLINE, Embase, Scopus, and Web of Science databases up to September 6, 2022, that addressed OBTX-A treatment for NDO following SCI were included. The quality of eligible studies was evaluated using Cochrane criteria. Also, the weighted mean difference (WMD) was measured with a random-effect model.

RESULTS

Regarding the overall efficacy after OBTX-A treatment in the short term, volume per void (VV) (WMD = 118.8, 95% CI: 90.9-146.7, p < 0.01), incontinence-quality of life (IQoL) (WMD = 24.3, 95% CI: 15.8-32.8, p < 0.01), and maximum cystometric capacity (MCC) (WMD = 144.5, 95% CI: 132.3 to 156.7, p < 0.01) significantly increased, while maximum detrusor pressure during storage (MDP) (WMD = -30.5, 95% CI: -35.9 to -25.1, p < 0.01) showed a significant decrease. Furthermore, compared to the placebo group at the 200-unit dose, there was a significant increase in MCC (WMD = 113.5, 95% CI: 84.7 to 142.3, p < 0.01) and a significant decrease in MDP (WMD = -27.2, 95% CI: -39.2 to -15.1, p < 0.01). Urinary tract infection (UTI), hematuria, and autonomic dysreflexia were the most common side effects, occurring at rates of 29.6%, 14.8%, and 13.4%, respectively.

CONCLUSION

Our findings highlighted the effectiveness and safety of OBTX-A as a promising treatment of NDO following SCI.

The Role of Botulinum Neurotoxin A in the Conservative Treatment of Fractures: An Experimental Study on Rats

This paper explores the role of botulinum neurotoxin in aiding fracture recovery through temporary muscle paralysis. Specifically, it investigates the effects of botulinum neurotoxin-induced paralysis of the sternocleidomastoid muscle on clavicle fractures in rats. The research aims to assess safety, effectiveness, and the impact on fracture healing. Healthy male Albino Wistar rats were divided into four groups: clavicle fracture, botulinum neurotoxin injection, both, and control. Surgeries were conducted under anaesthesia, and postoperatively, animals were monitored for 28 days. Euthanasia and radiological assessment followed, examining fracture healing and muscle changes, while tissues were histopathologically evaluated. The modified Lane-Sandhu scoring system was used for the radiographic evaluation of clavicle fractures, and the results varied from complete healing to nonunion. Histopathological examination at 28 days postfracture showed fibrous tissue, mesenchymal cells, and primary callus formation in all groups. Despite varied callus compositions, botulinum neurotoxin administration did not affect clavicle healing, as evidenced by similar scores to the control group. Several studies have explored botulinum neurotoxin applications in fracture recovery. Research suggests its potential to enhance functional recovery in certain types of fractures. Theoretical benefits include managing muscle spasticity, aiding reduction techniques, and preventing nonunion. However, botulinum neurotoxin's transient effect and nonuniversal applications should be considered. The present study found that botulinum toxin had no clear superiority in healing compared to controls, while histological evaluation showed potential adverse effects on muscle tissue. Further research is essential to understand its risk-benefit balance and long-term effects.

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

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

The Action of Botulinum Toxin A on the Sternocleidomastoid Muscle: An Experimental Study on Rats

In this study, we aim to investigate the effective dose of botulinum neurotoxin A that results in paralysis of the sternocleidomastoid muscle for a minimum duration of 28 days in Wistar rats. This research is the first in a series of studies to investigate the value of botulinum toxin A in the healing of clavicle fractures through the temporary paralysis of the sternocleidomastoid. A surgical incision was made under general anaesthesia, and botulinum neurotoxin A in respective doses of 4 and 6 international units (IU) or normal saline in equivalent volumes were injected directly into the exposed muscle. Electromyography was conducted on days 0, 7, and 28 following substance administration to determine the extent of muscle paralysis. Electromyography on day 0 showed no paralysis in either group. Animals injected with neurotoxin all exhibited paralysis on days 7 and 28 that was weaker in the group injected with the smaller dose of 4 IU. One death occurred in the group injected with the higher dose (6 IU), whereas in the control group, no paralysis was seen. Botulinum neurotoxin A in a dose of 6 IU resulted in complete paralysis of the sternocleidomastoid in rats for a minimum of 28 days. A dose of 4 IU resulted in less potent paralysis but was safer in our research. Botulinum neurotoxin is a substance utilised in cosmetics and therapeutics for many years, yet research shows that its use can be expanded to target a wider range of pathologies. In this series of studies, we aim to explore the neurotoxin's applications on the treatment of clavicle fractures. To investigate this, we need to first establish the duration of its action on the sternocleidomastoid muscle.

The Urothelium: Life in a Liquid Environment

The urothelium, which lines the renal pelvis, ureters, urinary bladder, and proximal urethra, forms a high-resistance but adaptable barrier that surveils its mechanochemical environment and communicates changes to underlying tissues including afferent nerve fibers and the smooth muscle. The goal of this review is to summarize new insights into urothelial biology and function that have occurred in the past decade. After familiarizing the reader with key aspects of urothelial histology, we describe new insights into urothelial development and regeneration. This is followed by an extended discussion of urothelial barrier function, including information about the roles of the glycocalyx, ion and water transport, tight junctions, and the cellular and tissue shape changes and other adaptations that accompany expansion and contraction of the lower urinary tract. We also explore evidence that the urothelium can alter the water and solute composition of urine during normal physiology and in response to overdistension. We complete the review by providing an overview of our current knowledge about the urothelial environment, discussing the sensor and transducer functions of the urothelium, exploring the role of circadian rhythms in urothelial gene expression, and describing novel research tools that are likely to further advance our understanding of urothelial biology.

Assessment of Anticholinergic Use After Fading of BTX-A Effects in Refractory Idiopathic Overactive Bladder: A Prospective Blinded Randomized Trial

PURPOSE

To evaluate the efficacy and safety of re-treatment with anticholinergics on refractory idiopathic overactive bladder (OAB) previously treated with intravesical botulinum neurotoxin type A (BTX-A) injections.

METHODS

One hundred patients were initially managed by intravesical injections of 100 IU of BTX-A. After the effects of BTX-A faded, patients were randomized into 2 groups: group A patients received solifenacin (10 mg) for 12 weeks (study group), while group B patients received placebo treatment for 12 weeks (control group), then subsequently received solifenacin (10 mg) for another 6 weeks. All patients underwent preoperative urodynamic testing. Patients were asked to complete the validated overactive bladder symptoms score (OABSS) and incontinence quality of life (I-QoL) instruments after the effects of intravesical BTX-A faded and at 12 weeks of follow-up. Univariate and multivariate analyses of the factors affecting treatment response were conducted.

RESULTS

At 12 weeks of follow-up, in group A, all OABSS items, including the total score, had improved significantly (P<0.0001). Group A had lower frequency and amplitude of detrusor overactivity and detrusor leak point pressure (P<0.0001, P=0.03, and P=0.01, respectively). Cystometric capacity also increased significantly (P=0.007), as did all I-QoL parameters. In a comparison of patients with failed treatment and patients with successful treatment, female sex, repeated intravesical BTX-A injections, and increased bladder capacity were statistically significant (P=0.001, P=0.0001, and P=0.002, respectively). Repeated intravesical BTX-A injections and increased bladder capacity were independent factors predicting treatment success.

CONCLUSION

In patients with refractory idiopathic OAB, reuse of anticholinergics could be an effective treatment option in patients after the effects of BTX-A fade. Repeated intravesical BTX-A injections and increased cystometric capacity could affect treatment response.

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.

Beta-3 adrenergic receptor is expressed in acetylcholine-containing nerve fibers of the human urinary bladder: An immunohistochemical study

AIMS

To identify in the human bladder the structures which express the Beta-3 adrenoceptor (β3AR).

METHODS

Human bladders from cadaveric organ donors (equally balanced in sex and age) were collected. Bladders were immediately fixed in paraformaldehyde and further processed for cryostat sectioning. Single and double immunohistochemistry was performed using antibodies against β3AR C-terminal, β3AR N-terminal, a pan-neuronal marker (β3-Tubulin) and markers of cholinergic (Vesicular Acetylcholine Transporter), adrenergic (Tyrosine Hidroxylase), and peptidergic (Calcitonin Gene-Related Peptide) nerve fibers.

RESULTS

Nerve fibers expressing immunoreactivity for β3AR were abundantly found in the mucosa and muscular layers of the human bladder. No β3AR-IR was detected on urothelial or smooth muscle cells. The presence of β3AR-IR in nerve fibers was confirmed by co-expression with β3-Tubulin. Nerve fibers expressing β3AR-IR were cholinergic, VAChT⁺ , and abundantly observed in the suburothelium. The cholinergic fibers were in close proximity and intermingled with adrenergic TH⁺ and peptidergic CGRP⁺ fibers.

CONCLUSIONS

We demonstrated that β3AR is abundantly located in acetylcholine-containing nerve fibers. These findings have important consequences to understand the mechanism of action of β3AR agonists currently used for the treatment of OAB.

M2muscarinic receptors inhibit cell proliferation and migration in urothelial bladder cancer cells

The role of muscarinic receptors in several diseases including cancer has recently emerged. To evaluate the hypothesis that muscarinic acetylcholine receptors may play a role in bladder cancer as well as in other tumor types, we investigated their expression in bladder tumor specimens. All examined samples expressed the M1, M2 and M3 receptor subtypes. We also found that the level of M2 transcripts, but not those of M1 or M3, significantly increased with the tumor histologic grade. In view of these results, we proceeded to investigate whether the M2 agonist Arecaidine had any effect on in vitro cell growth and migration of T24 cells, a bladder tumor cell line expressing the muscarinic receptors, including the M2 subtype. We observed that Arecaidine significantly reduced T24 and 5637 cell proliferation and migration in a concentration dependent manner. The silencing of M2 receptor by siRNA in T24 and 5637 cell lines showed the inability of Arecaidine (100 μM) to inhibit cell proliferation after 48 hours, whereas the use of M1 and M3 antagonists in T24 appeared not to counteract the Arecaidine effect, suggesting that the inhibition of cell proliferation was directly dependent on M2 receptor activation. These data suggest that M2 muscarinic receptors may play a relevant role in bladder cancer and represent a new attractive therapeutic target.

Retrograde transport of radiolabelled botulinum neurotoxin type A to the CNS after intradetrusor injection in rats

OBJECTIVE

To investigate the potential distribution of radiolabelled botulinum neurotoxin type A (BoNT/A) in the CNS after bladder injection in normal rats, by using the gamma-emitting radionuclide technetium-99 m ((99m) Tc).

MATERIALS AND METHODS

BoNT/A was radiolabelled by pretreatment with 2-iminothiolane and incubation with (99m) Tc-gluconate. The labelled toxin (99m) Tc-BoNT/A was purified using size exclusion HPLC. Twenty-four female Wistar rats were evenly injected in the bladder wall with either (99m) Tc-ΒοΝΤ/Α (n = 12) or free (99m) Tc (n = 12). Four rats from each group were killed at 1, 3 and 6 h after injection, respectively. The bladder, L6-S1 spinal cord segment and L6-S1 dorsal root ganglia (DRG) were harvested and their radioactivity counted in a gamma scintillation detector. Results were calculated as % injected dose (I.D.) per gram of tissue. The paired t-test was used for comparison of means of (99m) Tc-ΒοΝΤ/Α radioactivity vs free (99m) Tc in the tissues of interest.

RESULTS

Radiolabelled BoNT/A had a high radiochemical stability of 70% after 24 h. Gradual accumulation of (99m) Tc-ΒοΝΤ/Α was observed in the DRG up to 6 h after injection (P = 0.04 and P = 0.029 compared with 1 h and 3 h, respectively), while no accumulation was detected for free (99m) Tc. Consequently, (99m) Tc-ΒοΝΤ/Α radioactivity in the DRG was higher than free (99m) Tc radioactivity (3.18 ± 0.67% I.D./g vs 0.19 ± 0.10% I.D./g [P = 0.002] 6 h after injection). Values for (99m) Tc-ΒοΝΤ/Α radioactivity in the spinal cord were higher than those for free (99m) Tc, but not significantly. The bladder retained higher dosages of (99m) Tc-ΒοΝΤ/Α than free (99m) Tc at all time points.

CONCLUSIONS

Significant accumulation of the radiolabelled toxin in the lumbosacral DRG, together with a less significant uptake in the respective spinal cord segment as opposed to free radioactivity provide first evidence of the retrograde transport of BoNT/A to the CNS after bladder injection in rats.

γEpithelial Na(+) Channel (γENaC) and the Acid-Sensing Ion Channel 1 (ASIC1) expression in the urothelium of patients with neurogenic detrusor overactivity

OBJECTIVE

To investigate the expression of two types of cation channels, γEpithelial Na(+) Channel (γENaC) and the Acid-Sensing Ion Channel 1 (ASIC1), in the urothelium of controls and in patients affected by neurogenic detrusor overactivity (NDO). In parallel, urodynamic parameters were collected and correlated to the immunohistochemical results.

PATIENTS SUBJECTS AND METHODS

Four controls and 12 patients with a clinical diagnosis of NDO and suprasacral spinal cord lesion underwent urodynamic measurements and cystoscopy. Cold-cup biopsies were frozen and processed for immunohistochemistry and Western Blot. Spearman's correlation coefficient between morphological and urodynamic data was applied. One-way anova followed by Newman-Keuls multiple comparison post hoc test was applied for Western Blot results.

RESULTS

In the controls, γENaC and ASIC1 were expressed in the urothelium with differences in their cell distribution and intensity. In patients with NDO, both markers showed consistent changes either in cell distribution and labelling intensity compared with the controls. A significant correlation between a higher intensity of γENaC expression in the urothelium of patients with NDO and lower values of bladder compliance was detected.

CONCLUSIONS

The present findings show important changes in the expression of γENaC and ASIC1 in NDO human urothelium. Notably, while the changes in γENaC might impair the mechanosensory function of the urothelium, the increase of ASIC1 might represent an attempt to compensate for the excess in local sensitivity.

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

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

Experience with botulinum toxin type A in the treatment of neurogenic detrusor overactivity in clinical practice

Control of the lower urinary tract is a complex, multilevel process that involves both the peripheral and central nervous system. Neurogenic lower urinary tract dysfunction (LUTD) is a widespread chronic illness that impairs millions of people worldwide. Neurogenic LUTD has a major impact on quality of life, affecting emotional, social, sexual, occupational and physical aspects of daily life, and in addition to the debilitating manifestations for patients, it also imposes a substantial economic burden on every healthcare system. First-line treatment for neurogenic LUTD includes antimuscarinics and some form of catheterization, preferably intermittent self-catheterization. However, the treatment effect is often unsatisfactory, so that other options have to be considered. Moreover, neurogenic LUTD is a challenge because all available treatment modalities (i.e. conservative, minimally invasive and invasive therapies) may fail. In recent years, botulinum neurotoxin type A (BoNT/A) treatment has been shown to be an effective pharmacological therapy option in patients refractory to antimuscarinic and neurogenic detrusor overactivity (NDO). Several studies have shown that BoNT/A injection significantly reduces detrusor muscle overactivity. Also BoNT/A treatment of NDO has revealed a significant improvement of lower urinary tract function with regard to reduced urinary incontinence, reduced detrusor pressure, increased bladder capacity and improved quality of life in NDO.

Emerging treatments for overactive bladder: clinical potential of botulinum toxins

Overactive bladder (OAB) is a symptom syndrome including urgency, frequency, and nocturia - with or without incontinence. It is a common manifestation of detrusor overactivity (DO). DO is a urodynamic observation of spontaneous or provoked contractions of the detrusor muscle is seen during the filling phase of the micturition cycle. OAB is, therefore, both a motor and sensory disorder. Botulinum toxin is a purified form of the neurotoxin from Clostridium botulinum and has been used in medicine for many years. Over the last 10 years, it has been used for the treatment of DO and OAB when standard treatments, such as bladder training and oral anticholinergic medication, have failed to provide symptom relief. Botulinum toxin acts by irreversibly preventing neurotransmitter release from the neurons in the motor end plate and also at sensory synapses, although the clinical effect is not permanent due to the growth of new connections within treated tissues. It is known that botulinum toxin modulates vanillioid, purinergic, capsaicin, and muscarinic receptor expression within the lamina propria, returning them to levels seen in normal bladders. Clinically, the effect of botulinum toxin on symptoms of OAB and DO is profound, with large effects upon the symptom of urgency, and also large effects on frequency, nocturia, leakage episodes, and continence rates. These effects have been seen consistently within eight randomized trials and numerous case series. Botulinum toxin appears safe, with the only common side effect being that of voiding difficulty, occurring in up to 10% of treated patients. Dosing regimens are variable, depending on which preparation is used, but it is clear that dose recommendations have fallen over the last 5 years. There is limited evidence about the efficacy of repeat treatments. Botulinum toxin is an effective and safe second-line treatment for patients with OAB and DO.

Male incontinence: onabotulinum toxin A and sacral nerve stimulation

PURPOSE OF REVIEW

Overactive bladder affects 10-12% of men, of which 13% are refractory to medical therapy and seek second-line treatment. This places a substantial clinical and economic burden on the National Health Service United Kingdom.

RECENT FINDINGS

This review identifies current evidence for the use of onabotulinum toxin A and sacral nerve neuromodulation for the treatment of overactive bladder in patients who do not respond to optimal medical treatment. Posterior tibial nerve stimulation is not covered here. Clinical and financial implications of the treatments are reviewed.

SUMMARY

The focus will remain on recently published evidence, which may be useful to clinicians managing refractory patients.

Efficacy and safety of botulinum toxin A intradetrusor injections in adults with neurogenic detrusor overactivity/neurogenic overactive bladder: a systematic review

BACKGROUND

Botulinum toxin A (BoNTA) is increasingly used for therapy of neurogenic detrusor overactivity (NDO) refractory to antimuscarinics or where patients are experiencing antimuscarinic-related side effects.

OBJECTIVE

The objective was to compare and critically discuss the reported efficacy and safety of BoNTA in adults with neurogenic bladder dysfunction.

DATA SOURCES

Studies published between January 1985 and July 2012 were identified in the MEDLINE (PubMed) and SCOPUS databases.

STUDY SELECTION, STUDY APPRAISAL AND SYNTHESIS METHODS

A search for studies with onabotulinumtoxinA--the only formulation of BoNTA approved by the US FDA in adults with NDO--was performed. Exclusion criteria were urethral sphincter injection, no separate analysis between onabotulinumtoxinA and other formulations of BoNTA, mean follow-up ≤ 4 weeks and studies with ten or fewer patients. Clinical and urodynamic parameters for efficacy, adverse events (AEs) and tolerability were reviewed to offer recommendations for practice and future research.

RESULTS

A total of 28 included studies revealed superior effects of onabotulinumtoxinA compared with placebo in achieving continence, reducing incontinence episodes, improving urodynamic parameters and health-related quality of life. The most frequently reported AEs were de novo intermittent catheterization, urinary retention and asymptomatic urinary infection.

LIMITATIONS

Limitations of this review are the inclusion of studies with the level-3 evidence (22/28 studies), the heterogenicity of outcome parameters and time points chosen for follow-up reported in the reviewed studies.

CONCLUSIONS

OnabotulinumtoxinA therapy is effective, safe and well tolerated in adults with neurogenic bladder dysfunction. Further high-quality prospective trial data are required to determine the optimal dose, injection technique, long-term safety, favourable timing, indications for re-injections, and the impact of concomitant antimuscarinics on onabotulinumtoxinA therapy.

Effect of botulinum toxin A on urothelial-release of ATP and expression of SNARE targets within the urothelium

AIMS

Botulinum neurotoxin serotype A (BoNT/A) has emerged as an effective treatment of urinary bladder overactivity. Intravesical lipotoxin (BoNT/A delivery using liposomes), which may target the urothelium, is effective in blocking acetic acid induced hyperactivity in animals. The objective of this study was to assess the possible site of toxin action within the urothelium.

METHODS

We examined expression of the toxin receptor (SV2) and its cleavage targets (SNAP-25 and SNAP-23) within urothelium as well as effects of the toxin on mechanically evoked release of ATP from cultured rat urothelial cells. ATP release was measured using the luciferin-luciferase assay; we examined expression of SNAP-23 and -25 in urothelial cells and mucosa of rat and human bladders.

RESULTS

BoNT/A (1.5 U; 1-3 hr) blocked hypotonic evoked release of urothelial ATP, without affecting morphology. The expression of protein targets for BoNT/A binding (SV2) was detected in human and rat bladder mucosa and catalytic action (SNAP-23, -25) in urothelial cells and mucosa (differed in intensity) from rat and human bladder. Incubation of cultured (rat) urothelial cells with BoNT/A decreased expression levels of both SNAP-23 (44%) and SNAP-25 (80%).

CONCLUSIONS

Our findings reveal that the bladder urothelium expresses the intracellular targets and the binding protein for cellular uptake of BoNT/A; and that the toxin is able to suppress the levels of these targets as well as hypotonic-evoked ATP release. These data raise the possibility that intravesical treatment with BoNT/A suppresses bladder reflex and sensory mechanisms by affecting a number of urothelial functions including release of transmitters.

Intramural injection with botulinum toxin significantly elongates the pig esophagus

BACKGROUND/PURPOSE

Surgical treatment of long-gap esophageal atresia (LGEA) is challenging. Methods which facilitate stretching of the esophageal pouches may allow primary anastomosis. Botulinum toxin type A (BTX-A) blocks acetylcholine release in neuromuscular junctions, thereby causing muscle relaxation. We hypothesized that intramural injections with BTX-A into the esophageal wall of piglets would significantly elongate the tissue upon stretch.

METHODS

Twenty-four piglets were randomized to receive BTX-A of placebo (saline). After one hour, the esophagus was removed en bloc and tested in a stretch-tension device.

RESULTS

The mean esophageal elongation was 84% (range 83-101) in the BTX-A-group and 65% (50-78) in the control group. The mean difference between the two groups was 18%, which was significant (p < 0.001).

CONCLUSION

Intramural injections with botulinum toxin type A elongate the esophagus significantly. Clinically, this could be a potential method to achieve primary anastomosis in LGEA. Additional clinical studies are necessary to evaluate the method before it can be generally recommended.

New developments in the management of overactive bladder: focus on mirabegron and onabotulinumtoxinA

In the last few years, much new information has been generated on the pathophysiology, possible therapeutic targets, and pharmacologic treatment of overactive bladder (OAB). Antimuscarinic drugs are still first-line pharmacologic treatment for OAB and often have good initial response rates, but adverse effects and decreasing efficacy cause long-term compliance problems, prompting a search for new therapeutic alternatives. Mirabegron and onabotulinumtoxinA, two drugs with different mechanisms of action, and with adverse effect profiles different from those of antimuscarinics, were recently approved for treatment of OAB. However, their place in the treatment of this disorder has not yet been established. In this short review, the mechanisms of action, clinical efficacy, and safety profiles of these drugs are discussed and compared with those of the current gold standard, antimuscarinic agents.

Botulinum toxin-A for the treatment of overactive bladder: UK contributions

Background:

Botulinum toxin-A (BoNT/A) is now established second-line management for refractory overactive bladder (OAB) and recognised in many incontinence guidelines and pathways. For those with neurogenic detrusor overactivity secondary to spinal cord injury or multiple sclerosis, the toxin is currently licensed in certain parts of the world, including the UK. It is an effective treatment in those in whom antimuscarinics and conservative measures have failed who have symptoms of OAB and or detrusor overactivity (DO).

Methods:

Treatment can be given in an outpatient setting and can be administered under local anaesthesia. Its efficacy lasts for between six and 12 months.

Results:

It has an acceptable safety profile with the biggest risk being urinary tract infection and difficulty emptying the bladder, necessitating clean intermittent self-catheterisation (CISC). Medium-term follow-up suggests repeated injections are also safe and efficacious.

Conclusions:

The mechanism of action of the toxin is more complicated than originally thought, and it seems likely that it affects motor and sensory nerves of the bladder. In the last 10 years much of the progress of this treatment from early experimental trials to mainstream clinical use, and a better understanding of how it works in the bladder, are as a result of research conducted in the UK. This review summarises the significant and substantial evidence for BoNT/A to treat refractory OAB from UK centres.

Autonomic nervous control of the urinary bladder

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

Common theme for drugs effective in overactive bladder treatment: inhibition of afferent signaling from the bladder

The overactive bladder syndrome and detrusor overactivity are conditions that can have major effects on quality of life and social functioning. Antimuscarinic drugs are still first-line treatment. These drugs often have good initial response rates, but adverse effects and decreasing efficacy cause long-term compliance problems, and alternatives are needed. The recognition of the functional contribution of the urothelium/suburothelium, the autonomous detrusor muscle activity during bladder filling and the diversity of nerve transmitters involved has sparked interest in both peripheral and central modulation of overactive bladder syndrome/detrusor overactivity pathophysiology. Three drugs recently approved for treatment of overactive bladder syndrome/detrusor overactivity (mirabegron, tadalafil and onabotulinum toxin A), representing different pharmacological mechanisms; that is, β-adrenoceptor agonism, phosphodiesterase type 5 inhibition, and inhibition of nerve release of efferent and afferent transmitters, all seem to have one effect in common: inhibition of the afferent nervous activity generated by the bladder during filling. In the present review, the different mechanisms forming the pharmacological basis for the use of these drugs are discussed.

Alteration in TRPV1 and Muscarinic (M3) receptor expression and function in idiopathic overactive bladder urothelial cells

AIM

To examine function of both cholinergic (muscarinic) and TRPV1 receptors in human bladder urothelial (HBUC) from non-neurogenic overactive bladder (OAB) patients as compared to control subjects.

METHODS

Primary HBUC cultures were derived from cystoscopic biopsies from OAB and control subjects. Muscarinic and TRPV1 function was assessed by acetylcholine (5 μm) or capsaicin (0.5 μm) evoked ATP release, measured by luciferase assay. Overall, expression of TRPV1 and muscarinic M3 receptors in bladder urothelial cells was accomplished using western immunoblotting.

RESULTS

Our findings revealed that the response to acetylcholine in OAB HBUC cultures (which was blocked by the nonselective muscarinic antagonist, atropine methyl nitrate or AMN) was not significantly different than from controls. The acetylcholine M3 receptor was slightly decreased as compared to control. In contrast, OAB HBUC cultures exhibited a capsaicin hypersensitivity and augmented release of ATP (3.2 fold higher), which was blocked by the antagonist capsazepine. The increase in capsaicin sensitivity correlated with increased urothelial TRPV1 expression.

CONCLUSION

Though characterized in a small number of subjects, augmented release of urothelial-derived transmitters such as ATP could 'amplify' signalling between and within urothelial cells and nearby afferent nerves.

Botulinum neurotoxin serotype A suppresses neurotransmitter release from afferent as well as efferent nerves in the urinary bladder

BACKGROUND

Botulinum neurotoxin A (BoNTA), which alleviates overactive bladder symptoms, is thought to act predominantly via the inhibition of transmitter release from parasympathetic nerves. However, actions at other sites such as afferent nerve terminals are possible.

OBJECTIVE

To evaluate the effects of BoNTA on bladder afferent neuropeptide release and firing.

DESIGN, SETTING, AND PARTICIPANTS

One side of the bladder of control and chronic (1-2 wk) spinal cord transected (SCT; T(8)-T(9)) adult female mice was injected with BoNTA (0.5 U/5 μl saline). After 48 h, bladders with L(6)-S(2) spinal nerves were prepared for in vitro recordings.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

In bladder preparations, tension and optical mapping of Ca(2+) transients were used to measure intrinsic contractions, those evoked by capsaicin or the electrical stimulation of spinal nerves. Afferent firing was evoked by stretch or intrinsic bladder contractions. The numbers of responding units and firing rates were measured. Animal numbers were used to detect moderate to large between-group differences based on Cohen's criteria. Two-way analysis of variance was used to test spatial/temporal differences in Ca(2+) signals as mean plus or minus standard deviation. Differences between data sets were tested with the student t test and skewed data sets with a Mann-Whitney U test (significant when p<0.05).

RESULTS AND LIMITATIONS

In control and SCT bladders, BoNTA treatment decreased the contractions evoked by electrical stimulation of spinal nerves without altering intrinsic contractions. Afferent firing on untreated sides in response to stretch/intrinsic contractions was increased in SCTs versus controls. On BoNTA-treated sides, afferent firing rates were greatly attenuated in response to mechanical stimulation as were the capsaicin-evoked optical signals mediated by neuropeptide release.

CONCLUSIONS

SCT caused an increased sensitivity of afferent nerves to mechanical stimulation that was reduced by BoNTA treatment. Increased intrinsic activity after SCT was unaffected by the toxin. Thus BoNTA suppresses neurogenic detrusor overactivity by targeting afferent as well as efferent pathways in the bladder.

How does the urothelium affect bladder function in health and disease? ICI-RS 2011

The urothelium is a multifunctional tissue that not only acts as a barrier between the vesical contents of the lower urinary tract and the underlying tissues but also acts as a sensory organ by transducing physical and chemical stresses to the attendant afferent nervous system and underlying smooth muscle. This review will consider the nature of the stresses that the urothelium can transduce; the transmitters that mediate the transduction process; and how lower urinary pathologies, including overactive bladder syndrome, painful bladder syndrome and bacterial infections, are associated with alterations to this sensory system. In particular, the role of muscarinic receptors and the TRPV channels system will be discussed in this context. The urothelium also influences the contractile state of detrusor smooth muscle, both through modifying its contractility and the extent of spontaneous activity; potential pathways are discussed. The potential role that the urothelium may play in bladder underactivity is introduced, as well as potential biomarkers for the condition that may cross the urothelium to the urine. Finally, consideration is given to vesical administration of therapeutic agents that influence urinary tract function and how the properties of the urothelium may determine the effectiveness of this mode of delivery.

Researching bladder afferents-determining the effects of β(3) -adrenergic receptor agonists and botulinum toxin type-A

A substantial portion of the current research on lower urinary tract dysfunction is focused on afferent mechanisms. The main goals are to define and modulate the signaling pathways by which afferent information is generated, enhanced and conveyed to the central nervous system. Alterations in bladder afferent mechanisms are a potential source of voiding dysfunction and an emerging source for drug targets. Established drug therapies such as muscarinic receptor antagonists, and two emerging therapies, β(3) -adrenergic receptor agonists and botulinum toxin type-A, may act partly through afferent mechanisms. This review focuses on these two new principles and new and established methods for determining their sites of action. It also provides brief information on the innervation of the bladder, afferent receptors and transmitters and how these may communicate with the urothelium, interstitial cells and detrusor smooth muscle to regulate micturition. Peripheral and central mechanisms of afferent sensitization and myogenic mechanisms that lead to detrusor overactivity, overactive bladder symptoms and urgency sensations are also covered. This work is the result from 'Think Tank' presentations, and the lengthy discussions that followed, at the 2010 International Consultation on Incontinence Research Society meeting in Bristol, UK.

Effects of botulinum toxin type a in the bladder wall of children with neurogenic bladder dysfunction: a comparison of histological features before and after injections

PURPOSE

Botulinum toxin type A has gained popularity in urology. Most reported studies have been in adults at urology centers and most have addressed long-term safety. Since botulinum toxin type A treatment for neurogenic bladder dysfunction requires repeat injections, verifying that such treatment does not induce fibrosis in children seems essential.

MATERIALS AND METHODS

The study was approved by the institutional review board and patients were enrolled after we obtained written consent. Patients with neurogenic bladder dysfunction not responding to conventional treatment (anticholinergics and clean intermittent catheterization) were treated with 10 IU/kg botulinum toxin type A up to a maximum of 300 IU. Endoscopic cold cup biopsies were obtained from the posterolateral bladder wall 1.5 to 2 cm above the ureteral orifice. Bladder wall findings were categorized into 3 groups, including inflammatory infiltration, edema and fibrosis. Each criterion was then graded as mild or severe and analyzed by Fisher's exact test (p <0.05).

RESULTS

A total of 46 bladder wall biopsies were obtained from 40 patients 2 to 18 years old. Biopsies were evaluated in groups 1 and 2, including group 1-20 from patients with no botulinum toxin type A injection and group 2-20 after botulinum toxin type A injection. Group 2 was subdivided into group 3-10 biopsies after 1 injection and group 4-10 after multiple injections. Six patients underwent biopsy twice, that is before the first and second treatments. Histological changes were present in all biopsies. When comparing groups 1 and 2, there was no statistically significant difference in inflammation and edema. However, there was a significant difference in fibrosis between groups 1 and 4 (p <0.05) with apparently decreased fibrosis after multiple injections.

CONCLUSIONS

In our experience repeat botulinum toxin type A injections into the detrusor in children do not lead to increased fibrosis in the bladder wall. This study confirms the long-term safety of botulinum toxin type A in the pediatric population.