Effect of botulinum toxin on expression of nerve growth factor and transient receptor potential vanilloid 1 in urothelium and detrusor muscle of rats with bladder outlet obstruction-induced detrusor overactivity

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.

Slow development of bladder malfunction parallels spinal cord fiber sprouting and interneurons' loss after spinal cord transection

Neurogenic lower urinary tract dysfunction typically develops after spinal cord injury. We investigated the time course and the anatomical changes in the spinal cord that may be causing lower urinary tract symptoms following injury. Rats were implanted with a bladder catheter and external urethral sphincter electromyography electrodes. Animals underwent a large, incomplete spinal transection at the T8/9 spinal level. At 1, 2-3, and 4 weeks after injury, the animals underwent urodynamic investigations. Urodynamic investigations showed detrusor overactivity and detrusor-sphincter-dyssynergia appearing over time at 3-4 weeks after injury. Lower urinary tract dysfunction was accompanied by an increase in density of C-fiber afferents in the lumbosacral dorsal horn. CRF-positive Barrington's and 5-HT-positive bulbospinal projections drastically decreased after injury, with partial compensation for the CRF fibers at 3-4 weeks. Interestingly, a decrease over time was observed in the number of GABAergic neurons in the lumbosacral dorsal horn and lamina X, and a decrease of glutamatergic cells in the dorsal horn. Detrusor overactivity and detrusor-sphincter-dyssynergia might therefore arise from a discrepancy in inhibitory/excitatory interneuron activity in the lumbosacral cord as well as input changes which develop over time after injury. The processes point to spinal plastic changes leading to malfunction of the important physiological pathway of lower urinary tract control.

Botulinum toxin A improves neurogenic bladder fibrosis by suppressing transforming growth factor β1 expression in rats

Background

Intradetrusor botulinum toxin A injection is recommended for the treatment of refractory detrusor overactivity (DO) in patients with neurogenic bladder, however, whether it could inhibit neurogenic bladder fibrosis is uncertain. This study aimed to investigate the effect of botulinum toxin A on neurogenic bladder fibrosis and the underlying mechanism.

Methods

Forty eight Female Wistar rats were evenly randomized into 4 groups: Sham, T10 transection, Early and Late groups. The last three groups were subjected to T10 spinal cord transection, while the Sham group was treated with sham surgery. 0.9% saline was injected into the detrusor in the Sham and T10 transection groups simultaneously with the surgery, while 2 U/rat botulinum toxin A was injected into the detrusor simultaneously with the surgery in the Early group and 4 weeks following the surgery in the Late group. Body/bladder weight, cystometric parameters, bladder Hematoxylin-eosin staining were used to evaluate the bladder fibrosis. Western blot and quantitative Real-time PCR were used to evaluate the expression of bladder transforming growth factor β1.

Results

Compared with the T10 transection group, the bladder/body weight was decreased significantly in the Early and Late groups (P<0.05), along with the significant inhibition of non-voiding contraction (NVC) frequency and amplitude (P<0.05), and the significant increase of bladder volume (P<0.05). The detrusor connective tissue percentage (P<0.05) and the expression of transforming growth factor β1 (P<0.05) also decreased significantly in the Early and Late groups. Those changes were more obviously in the Early group than in the Late group.

Conclusions

Intradetrusor botulinum toxin A injection reduced bladder fibrosis in rats with spinal cord injury (SCI), which was more obviously in the Early group than in the Late group. The mechanisms might be mediated by suppression of transforming growth factor β1 (TGF-β1) expression.

Emerging roles of the TRPV4 channel in bladder physiology and dysfunction

The transient receptor potential vanilloid type 4, TRPV4, is a polymodal cation channel which can be activated by diverse stimuli including mechanical, thermal and chemical cues. In the urinary bladder, TRPV4 is not only abundantly expressed in the urothelium but may also be localized in subepithelium, detrusor smooth muscles and afferent neurons. Emerging evidence indicates that the TRPV4 channel plays a sensory role in the uroepithelium, where it may regulate the release of sensory mediators such as ATP, which in turn modulates afferent nerve activity in response to bladder filling during the urination cycle. TRPV4 may also directly regulate detrusor contractility and the urothelial barrier function. Altered TRPV4 expression has been detected in various pathological bladder conditions. As such, TRPV4 may be a promising therapeutic target for bladder dysfunctions.

Botulinum toxin in low urinary tract disorders - over 30 years of practice (Review)

Botulinum toxin is a substance produced by Clostridium Botulinum and is responsible for human botulism. This substance is a poison, a neurotoxin, but used in limited quantities it can be a cure for some diseases. It is well connected to a large variety of medical applications. The mechanism of action relies on blocking the acetylcholine at the neuromuscular junction, which blocks the transmission of the nervous impulse with secondary flaccid paralysis. In urology, its role in idiopathic overactive bladder and neurogenic bladder is well known. We performed a thorough review using PubMed and other databases, revising the mechanisms of botulinum toxin action in urologic pathology, treatment procedures and other options. Botulinum toxin is a well-studied substance with a large number of applications in medicine. In urologic pathology, overactive bladder and neurogenic bladder are backed by robust studies that support the therapeutic role of this substance. The toxin has multiple effects, such as inhibition of the nerve growth factor, blocking the bladder sensory afferent pathway and apoptotic effect on the prostate tissue, by inhibiting the substance P, altering the nociceptive pathways. Interstitial cystitis and other rare pathologies show promising results, but further studies are needed. The role of botulinum toxin in benign prostatic hyperplasia is still not elucidated.

The Pharmacological Mechanism of Diabetes Mellitus-Associated Overactive Bladder and Its Treatment with Botulinum Toxin A

Diabetes mellitus (DM) is an independent risk factor for overactive bladder (OAB). The pathophysiology of DM-associated OAB is multifactorial and time-dependent. Diabetic bladder dysfunction is highly associated with diabetic complications, mainly including diabetic neuropathy and atherosclerosis. Chronic systemic inflammation and bladder urothelial inflammation may contribute to the onset of OAB. Intravesical botulinum toxin A (BoNT-A) injection has proved to be a successful treatment for idiopathic and neurogenic OAB. BoNT-A can inhibit the efferent pathways of the bladder as well as the chronic inflammation and hypersensitivity via the afferent pathways. We conducted a review of the published literature in Pubmed using a combination of two keywords, namely “botulinum toxin A” (BoNT-A) and “overactive bladder”, with or without the additional keywords “detrusor overactivity”, “diabetes mellitus”, “inflammation”, and “urodynamic study”. We also reviewed the experience of our research teams, who have published several studies of the association between DM and OAB. Since limited data support the effectiveness and safety of BoNT-A for treating patients with DM-associated OAB, a comprehensive evaluation of diabetic complications and urodynamic study is needed before treatment. In the future, it is imperative to explore the clinical characteristics and inflammatory biomarkers of diabetes as determining predictors of the treatment efficacy.

Cancer survivorship issues with radiation and hemorrhagic cystitis in gynecological malignancies

PURPOSE

Given that more cancers are being diagnosed earlier and that treatment of cancer is improving, health issues of cancer survivors are becoming more common and apparent. Pelvic radiation therapy for the treatment of gynecological cancers can lead to long-term collateral damage to the bladder, a condition termed radiation cystitis (RC). Late sequelae may take many years to develop and include incontinence and pain as well as hematuria. RC is a rare but potentially life-threatening condition for which there are few management and treatment options.

METHODS

There are limited data in the literature regarding the effects of radiation on the bladder after gynecological cancer therapy and we hereby review the literature on cancer survivorship issues of pelvic radiation for gynecology literature.

RESULTS

Treatment options are available for patients with radiation-induced hemorrhagic cystitis. However, most treatments are risky or only effective for a short timeframe and no therapy is currently available to reverse the disease progress. Furthermore, no standardized guidelines exist describing preferred management options. Common therapies include hyperbaric oxygen therapy, clot evacuation, fulguration, intravesical instillation of astringent agents, and surgery. Novel developing strategies include Botulinum Toxin injections and liposomal-tacrolimus instillations. These treatments and strategies are discussed.

CONCLUSIONS

In this review, we will present current and advanced therapeutic strategies for RC to help cancer survivors deal with long-term bladder health issues.

New frontiers in molecular and imaging research on evaluation and diagnosis of bladder outlet obstruction in women

Purpose

Diagnosis of bladder outlet obstruction (BOO) often presents a challenge in female patients. Traditional diagnostic elements such as symptom history and urodynamic data are rarely clear cut in women. Therefore, we sought to review the current literature on diagnosis of female BOO, focusing on new frontiers in the realm of molecular markers and imaging modalities.

Recent Findings

In addition to fluoroscopy in the setting of videourodynamics, ultrasound and MRI can augment the diagnosis and aid in therapeutic planning in certain etiologies of female BOO. Furthermore, multiple potential biomarkers (i.e. nerve growth factor, prostaglandins, ATP) that have been studied in correlation to BOO in animal models as well as human subjects hold promise for diagnostic applications.

Summary

These novel techniques may augment standard clinical and urodynamic evaluation of BOO in females. Future directions include further studies of each of these biomarkers in female patients with BOO compared to normal controls to test their feasibility as potential screening tools.

Benefits and limitations of animal models in partial bladder outlet obstruction for translational research

The functions of the lower urinary tract have been investigated for more than a century. Lower urinary tract symptoms, such as incomplete bladder emptying, weak urine stream, daytime urinary frequency, urgency, urge incontinence and nocturia after partial bladder outlet obstruction, is a frequent cause of benign prostatic hyperplasia in aging men. However, the pathophysiological mechanisms have not been fully elucidated. The use of animal models is absolutely imperative for understanding the pathophysiological processes involved in bladder dysfunction. Surgical induction has been used to study lower urinary tract functions of numerous animal species, such as pig, dog, rabbit, guinea pig, rat and mouse, of both sexes. Several morphological and functional modifications under partial bladder outlet obstruction have not only been observed in the bladder, but also in the central nervous system. Understanding the changes of the lower urinary tract functions induced by partial bladder outlet obstruction would also contribute to appropriate drug development for treating these pathophysiological conditions. In the present review, we discuss techniques for creating partial bladder outlet obstruction, the characteristics of several species, as well as issues of each model, and their translational value.

Constitutive expression Of NGF And P75(NTR) affected by bladder distension and NGF antisense treatment

AIMS

It is known that bladder exposure to noxious stimuli elicits nerve growth factor (NGF) expression with region wise differences. Here, we investigated the effect of bladder distension (cystometry) and bladder wall injection of NGF antisense oligonucleotide (ODN) together as well as separately on spontaneous (constitutive) expression of NGF and its cognate p75 neurotrophin receptor (p75(NTR)).

METHOD

Under isoflurane anesthesia, either 15μg of protamine sulfate (vehicle) alone or complexed with 1.5μg of NGF antisense or scrambled ODN was injected (10μL) at 4 sites in bladder wall of 24 adult female Sprague-Dawley rats and 6 rats were left untreated (n=30). Under urethane anesthesia, cystometry (CMG) was performed in treated and control rats. Fluorescent ODN and NGF/p75(NTR) expression was localized in harvested tissue.

KEY FINDINGS

Complexation of ODN with protamine was essential for the retention of ODN in bladder tissue as the uncomplexed ODN was untraceable after injection. Bladder distension from CMG raised the expression of NGF and p75(NTR) relative to CMG naïve rats. The groups treated with vehicle, scrambled and antisense ODN were indistinct with regard to CMG parameters, but the intense immunoreactivity of NGF and p75(NTR) seen in the vehicle and scrambled ODN groups was reduced following treatment with NGF antisense.

SIGNIFICANCE

The constitutive expression of NGF and p75(NTR) is responsive to bladder distension and administration of NGF antisense. Complexation with protamine reduces the clearance of ODN and demonstrates the potential of ODN nanoparticles as an option for reducing the inducible NGF expression in OAB patients following intradetrusor injection.

Treatment of painful bladder syndrome/interstitial cystitis with botulinum toxin A: why isn't it effective in all patients?

Botulinum toxin A (BTA) is currently used to treat a variety of painful disorders, including painful bladder syndrome/interstitial cystitis (PBS/IC). However, BTA is not consistently effective in all patients. This may be due to the disparity of causes of pain, but this may also relate to the processes by which BTA exerts anti-nociceptive effects. This review discusses mechanisms by which BTA may inhibit pain and studies of the use of BTA in PSB/IC patients. It is doubtful that any single treatment will effectively control pain in PBS/IC patients, and it is highly probable that multiple strategies will be required, both within individual patients and across the population of PBS/IC patients. The purpose of this review is to discuss those mechanisms by which BTA acts, with the intent that alternative strategies exploiting these mechanism, or work through alternative pathways, can be identified to more effectively treat pain in PBS/IC patients in the future.

Structural and Functional Interactions between Transient Receptor Potential Vanilloid Subfamily 1 and Botulinum Neurotoxin Serotype A

BACKGROUND

Botulinum neurotoxins are produced by Clostridium botulinum bacteria. There are eight serologically distinct botulinum neurotoxin isoforms (serotypes A-H). Currently, botulinum neurotoxin serotype A (BoNT⁄A) is commonly used for the treatment of many disorders, such as hyperactive musculoskeletal disorders, dystonia, and pain. However, the effectiveness of BoNT⁄A for pain alleviation and the mechanisms that mediate the analgesic effects of BoNT⁄A remain unclear. To define the antinociceptive mechanisms by which BoNT/A functions, the interactions between BoNT⁄A and the transient receptor potential vanilloid subfamily 1 (TRPV1) were investigated using immunofluorescence, co-immunoprecipitation, and western blot analysis in primary mouse embryonic dorsal root ganglion neuronal cultures.

RESULTS

1) Three-week-old cultured dorsal root ganglion neurons highly expressed transient TRPV1, synaptic vesicle 2A (SV2A) and synaptosomal-associated protein 25 (SNAP-25). SV2A and SNAP-25 are the binding receptor and target protein, respectively, of BoNT⁄A. 2) TRPV1 colocalized with both BoNT⁄A and cleaved SNAP-25 when BoNT⁄A was added to dorsal root ganglia neuronal cultures. 3) After 24 hours of BoNT⁄A treatment (1 nmol⁄l), both TRPV1 and BoNT⁄A positive bands were detected in western blots of immunoprecipitated pellets. 4) Blocking TRPV1 with a specific antibody decreased the cleavage of SNAP-25 by BoNT⁄A.

CONCLUSION

BoNT/A interacts with TRPV1 both structurally and functionally in cultured mouse embryonic dorsal root ganglion neurons. These results suggest that an alternative mechanism is used by BoNT⁄A to mediate pain relief.

Challenges and Opportunities in Radiation-induced Hemorrhagic Cystitis

As diagnosis and treatment of cancer is improving, medical and social issues related to cancer survivorship are becoming more prevalent. Hemorrhagic cystitis (HC), a rare but serious disease that may affect patients after pelvic radiation or systemic chemotherapy, has significant unmet medical needs. Although no definitive treatment is currently available, various interventions are employed for HC. Effects of nonsurgical treatments for HC are of modest success and studies aiming to control radiation-induced bladder symptoms are lacking. In this review, we present current and advanced therapeutic strategies for HC to help cancer survivors deal with long-term urologic health issues.

The NLRP3 Inflammasome Mediates Inflammation Produced by Bladder Outlet Obstruction

PURPOSE

While bladder outlet obstruction is well established to elicit an inflammatory reaction in the bladder that leads to overactive bladder and fibrosis, little is known about the mechanism by which this is initiated. NLRs (NOD-like receptors) and the structures that they form (inflammasomes) have been identified as sensors of cellular damage, including pressure induced damage, and triggers of inflammation. Recently we identified these structures in the urothelium. In this study we assessed the role of the NLRP3 (NACHT, LRR and PYD domains-containing protein 3) inflammasome in bladder dysfunction resulting from bladder outlet obstruction.

MATERIALS AND METHODS

Bladder outlet obstruction was created in female rats by inserting a 1 mm outer diameter transurethral catheter, tying a silk ligature around the urethra and removing the catheter. Untreated and sham operated rats served as controls. Rats with bladder outlet obstruction were given vehicle (10% ethanol) or 10 mg/kg glyburide (a NLRP3 inhibitor) orally daily for 12 days. Inflammasome activity, bladder hypertrophy, inflammation and bladder function (urodynamics) were assessed.

RESULTS

Bladder outlet obstruction increased urothelial inflammasome activity, bladder hypertrophy and inflammation, and decreased voided volume. Glyburide blocked inflammasome activation, reduced hypertrophy and prevented inflammation. The decrease in voided volume was also attenuated by glyburide mechanistically as an increase in detrusor contraction duration and voiding period.

CONCLUSION

Results suggest the importance of the NLRP3 inflammasome in the induction of inflammation and bladder dysfunction secondary to bladder outlet obstruction. Arresting these processes with NLRP3 inhibitors may prove useful to treat the symptoms that they produce.

Effect of the Chinese traditional prescription Suo Quan Wan on TRPV1 expression in the bladder of rats with bladder outlet obstruction

Background

Suo Quan Wan (SQW) is a Chinese traditional prescription that has been used in clinical treatment of lower urinary tract symptoms for centuries. However, scientific basis of SQW efficacy and mechanism is still needed. This study investigated the effect of SQW on bladder function and transient receptor potential vanilloid 1 (TRPV1) expression in the bladder of rats with bladder outlet obstruction (BOO). The induced changes in bladder function in overactive bladder (OAB) rat model were observed following different periods of outlet obstruction to obtain an appropriate rat model.

Methods

This study was carried out in two parts. In the first part, female Sprague–Dawley rats received sham operations or partial BOO operations. Two, four, and six weeks later, the OAB model groups and control were subjected to urodynamic tests to measure differences in bladder functions. Once the appropriate rat model was obtained, the second part of the experiment was performed. The rat model was recreated and treated with SQW. Urodynamic assessment was conducted, and the bladders of the rats were then removed. Immunofluorescence staining, real-time PCR, and Western blot were performed to localize and quantify the expression of TRPV1 in the bladder.

Results

Results of the first part indicated that at 2 and 4 weeks, the OAB model group exhibited significant differences in urodynamic parameters, including bladder pressure, maximum voiding pressure, and maximum bladder capacity, compared with the sham group. At 4 and 6 weeks, the OAB model group exhibited significant differences in residual volume (RV) and non-voiding contraction frequency. Six-week OAB model group showed much more RV but less voiding efficiency when compared with 6-week sham group or 2—and 4-week OAB model group. Rats that underwent BOO exhibited similarities with the compensated state before four weeks and may have entered decompensated state at six weeks. Studies conducted with 4-week OAB model were appropriate.

In part two of the experiment, unstable bladder in the OAB model group recovered bladder stability after SQW treatment, accompanied by improved bladder hypertrophy, as well as corrected urodynamic parameters. Expression of TRPV1 mRNA and proteins in the bladder was significantly greater in the OAB model group than that in the control group, which subsequently decreased significantly with SQW treatment in BOO-induced rats.

Conclusions

SQW can modulate the expression of TRPV1 in accordance with the recovery of bladder function.

Electronic supplementary material

The online version of this article (doi:10.1186/s12906-015-0898-7) contains supplementary material, which is available to authorized users.

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.

Research Findings on Overactive Bladder

Several physiopathologic conditions lead to the manifestation of overactive bladder (OAB). These conditions include ageing, diabetes mellitus, bladder outlet obstruction, spinal cord injury, stroke and brain injury, Parkinson's disease, multiple sclerosis, interstitial cystitis, stress and depression. This review has discussed research findings in human and animal studies conducted on the above conditions. Several structural and functional changes under these conditions have not only been observed in the lower urinary tract, but also in the brain and spinal cord. Significant changes were observed in the following areas: neurotransmitters, prostaglandins, nerve growth factor, Rho-kinase, interstitial cells of Cajal, and ion and transient receptor potential channels. Interestingly, alterations in these areas showed great variation in each of the conditions of the OAB, suggesting that the pathophysiology of the OAB might be different in each condition of the disease. It is anticipated that this review will be helpful for further research on new and specific drug development against OAB.

Analgesic effects of botulinum neurotoxin type A in a model of allyl isothiocyanate- and capsaicin-induced pain in mice

We evaluate analgesic effects of BoNT/A in relation to the two main transient receptor potentials (TRP), the vanilloid 1 (TRPV1) and the ankyrin 1 (TRPA1), having a role in migraine pain. BoNT/A (15 pg/mouse) was injected in the inner side of the medial part of hindlimb thigh of mice, where the superficial branch of femoral artery is located. We chosen this vascular structure because it is similar to other vascular structures, such as the temporal superficial artery, whose perivascular nociceptive fibres probably contributes to migraine pain. After an interval, ranging from 7 to 30 days, capsaicin (agonist of TRPV1) or allyl isothiocyanate (AITC; agonist of TRPA1) were injected in the same region previously treated with BoNT/A and nocifensive response to chemicals-induced pain was recorded. In absence of BoNT/A, capsaicin and AITC induced extensive nocifensive response, with a markedly different temporal profile: capsaicin induced maximal pain during the first 5 min, while AITC induced maximal pain at 15-30 min after injection. Pretreatment with BoNT/A markedly reduced both the capsaicin- and AITC-induced pain for at least 21 days. These data suggest a long lasting analgesic effect of BoNT/A exerted via prevention of responsiveness of TRPV1 and TRPA1 toward their respective agonists.

Neurotrophins, endocannabinoids and thermo-transient receptor potential: a threesome in pain signalling

Because of the social and economic costs of chronic pain, there is a growing interest in unveiling the cellular and molecular mechanisms underlying it with the aim of developing more effective medications. Pain signalling is a multicomponent process that involves the peripheral and central nervous systems. At the periphery, nociceptor sensitisation by pro-inflammatory mediators is a primary step in pain transduction. Although pain is multifactorial at cellular and molecular levels, it is widely accepted that neurotrophin (TrkA, p75NTR, Ret and GFRs), cannabinoid (CB1 and CB2), and thermo-transient receptor potential (TRPs; TRPV1, TRPA1 and TRPM8) receptors play a pivotal role. They form a threesome for which endocannabinoids appear to be a first line of defence against pain, while neurotrophins and thermoTRPs are the major generators of painful signals. However, endocannabinoids may exhibit nociceptive activity while some neurotrophins may display anti-nociception. Accordingly, a clear-cut knowledge of the modulation and context-dependent function of these signalling cascades, along with the molecular and dynamic details of their crosstalk, is critical for understanding and controlling pain transduction. Here, the recent progress in this fascinating topic, as well as the tantalizing questions that remain unanswered, will be discussed. Furthermore, we will underline the need for using a systems biology approach (referred to as systems pain) to uncover the dynamics and interplay of these intricate signalling cascades, taking into consideration the molecular complexity and cellular heterogeneity of nociceptor populations. Nonetheless, the available information confirms that pharmacological modulation of this signalling triad is a highly valuable therapeutic strategy for effectively treating pain syndromes.

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.

TRP channels in lower urinary tract dysfunction

Lower urinary tract dysfunction (LUTd) represents a major healthcare problem. Although it is mostly not lethal, associated social disturbance, medical costs, loss of productivity and especially diminished quality of life should not be underestimated. Although more than 15% of people suffer from a form of LUTd to some extent, pathophysiology often remains obscure. In the past 20 years, transient receptor potential (TRP) channels have become increasingly important in this field of research. These intriguing ion channels are believed to be the main molecular sensors that generate bladder sensation. Therefore, they are intensely pursued as new drug targets for both curative and symptomatic treatment of different forms of LUTd. TRPV1 was the first of its class to be investigated. Actually, even before this channel was cloned, it had already been targeted in the bladder, with clinical trials of intravesical capsaicin instillations. Several other polymodally gated TRP channels, particularly TRPM8, TRPA1 and TRPV4, also appear to play a prominent role in bladder (patho)physiology. With this review, we provide a brief overview of current knowledge on the role of these TRP channels in LUTd and their potential as molecular targets for treatment.

Neural mechanisms underlying lower urinary tract dysfunction

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

Down-regulation of nerve growth factor expression in the bladder by antisense oligonucleotides as new treatment for overactive bladder

PURPOSE

Nerve growth factor over expression in the bladder has a role in overactive bladder symptoms via the mediation of functional changes in bladder afferent pathways. We studied whether blocking nerve growth factor over expression in bladder urothelium by a sequence specific gene silencing mechanism would suppress bladder overactivity and chemokine expression induced by acetic acid.

MATERIALS AND METHODS

Female Sprague-Dawley® rats anesthetized with isoflurane were instilled with 0.5 ml saline, scrambled or TYE™ 563 labeled antisense oligonucleotide targeting nerve growth factor (12 μM) alone or complexed with cationic liposomes for 30 minutes. The efficacy of nerve growth factor antisense treatments for acetic acid induced bladder overactivity was assessed by cystometry. Bladder nerve growth factor expression levels and cellular distribution were quantified by immunofluorescence staining and enzyme-linked immunosorbent assay. Effects on bladder chemokine expression were measured by Luminex® xMAP® analysis.

RESULTS

Liposomes were needed for bladder uptake of oligonucleotide, as seen by the absence of bright red TYE 563 fluorescence in rats instilled with oligonucleotide alone. At 24 hours after liposome-oligonucleotide treatment baseline bladder activity during saline infusion was indistinct in the sham and antisense treated groups with a mean ± SEM intercontraction interval of 348 ± 55 and 390 ± 120 seconds, respectively. Acetic acid induced bladder overactivity was shown by a decrease in the intercontraction interval to a mean of 33.2% ± 4.0% of baseline in sham treated rats. However, the reduction was blunted to a mean of 75.8% ± 3.4% of baseline in rats treated with liposomal antisense oligonucleotide (p <0.05). Acetic acid induced increased nerve growth factor in the urothelium of sham treated rats, which was decreased by antisense treatment, as shown by enzyme-linked immunosorbent assay and reduced nerve growth factor immunoreactivity in the urothelium. Increased nerve growth factor in bladder tissue was associated with sICAM-1, sE-selectin, CXCL-10 and 1, leptin, MCP-1 and vascular endothelial growth factor over expression, which was significantly decreased by nerve growth factor antisense treatment (p <0.01).

CONCLUSIONS

Acetic acid induced bladder overactivity is associated with nerve growth factor over expression in the urothelium and with chemokine up-regulation. Treatment with liposomal antisense suppresses bladder overactivity, and nerve growth factor and chemokine expression. Local suppression of nerve growth factor in the bladder could be an attractive approach for overactive bladder. It would avoid the systemic side effects that may be associated with nonspecific blockade of nerve growth factor expression.

Expression of transient receptor potential vanilloid 4 and effects of ruthenium red on detrusor overactivity associated with bladder outlet obstruction in rats

PURPOSE

To investigate transient receptor potential vanilloid 4 (TRPV4) expression and the effects of ruthenium red (RR)-TRPV antagonist-on detrusor overactivity (DO) associated with bladder outlet obstruction (BOO).

METHODS

Rats were randomly assigned to 3 groups. The control group (n = 10) included sham-operated rats. The BOO-group without RR (n = 15) and BOO-group with RR (n = 15) underwent partial BOO surgery. Three weeks postoperatively, cystometrography was performed in all rats. After confirming DO, RR was instilled intravesically in the BOO-group with RR. Urodynamic parameters were investigated, including contraction interval (CI) and contraction pressure (CP). TRPV4 expression was evaluated through immunofluorescence staining and western blotting.

RESULTS

The BOO-group without RR had significantly shorter CI and significantly higher CP compared to the control. In the BOO-group with RR, CI was significantly longer compared to the BOO-group without RR. However, change in CP between BOO-group without and with RR was not significantly different. Immunofluorescence staining showed that TRPV4 was localized in the urothelium and detrusor muscles. TRPV4 immunofluorescence signals were increased in the urothelium and detrusor muscle in BOO-group without RR, compared with the control. In western blot analysis, immunoreactive bands indicating expression of TRPV4 were detected in the urothelium and detrusor muscle, and those were significantly increased in the BOO-group without RR compared with the control in the urothelium and detrusor muscle.

CONCLUSIONS

TRPV4 plays an important role in the pathophysiology of DO, and RR has a beneficial effect on DO associated with BOO.

Nerve growth factor (NGF): a potential urinary biomarker for overactive bladder syndrome (OAB)?

WHAT'S KNOWN ON THE SUBJECT? AND WHAT DOES THE STUDY ADD?: The search for a biomarker in overactive bladder syndrome (OAB) is an emerging field of interest, as bladder dysfunction is a common complaint that causes significant morbidity. A biomarker may give us insight as a diagnostic tool, and also inform us about how severe the condition is, how it may progress and how it may best be treated. The protein of interest here is nerve growth factor (NGF) and it has been shown to be a dynamic molecule in the bladder of patients with OAB. Urinary levels have been seen to rise in patients with OAB and fall in those who respond to treatment. However, there have also been many studies that examine this trend in numerous other conditions, e.g. interstitial cystitis, bladder outflow obstruction, renal stone disease and patients with neurological impairment after stroke. As a result the specificity of this as a potential urinary biomarker for OAB is questioned. This is a review of published studies, which discusses the pros and cons of NGF as a potential urinary biomarker. The evidence is examined and the studies are summarised together in a Table. Questions remain about the reliability, practicality and specificity of NGF as a biomarker for OAB. These questions need to be addressed by further studies that could clarify the points raised.

OBJECTIVE

To review the current literature on the use of urinary nerve growth factor (NGF) as a potential biomarker for overactive bladder syndrome (OAB).

METHOD

A comprehensive electronic literature search was conducted using the PubMed database to identify publications relating to urinary NGF.

RESULTS

There are a growing number of publications that have measured urinary NGF levels in different types of bladder dysfunction. These range from OAB, bladder pain syndrome, idiopathic and neurogenic detrusor overactivity, bladder oversensitivity and bladder outflow obstruction. Urinary NGF levels do appear to be raised in these pathological states when compared with healthy control samples. In patients with OAB, these raised urinary NGF levels appear to also reduce after successful treatment with antimuscarinics and botulinum toxin A, which indicates a potential use in monitoring responses to treatment. However, raised levels are not limited to OAB, which questions its specificity. Urinary NGF measurements are performed with an enzyme-linked immunosorbent assay using polyclonal antibodies to NGF. The technique requires standardisation, and the different antibodies to NGF require validating. Also a definition of what is the 'normal' range of NGF in urine is still required before it can be used as a diagnostic and prognostic tool.

CONCLUSIONS

Whilst the evidence for an increased urinary NGF in OAB appears convincing, many questions about its validity remain including: specificity, sensitivity, cost- and time-effectiveness. Many criteria for what constitutes a biomarker still need to be evaluated and met before this molecule can be considered for this role.

Onabotulinumtoxin-A intradetrusorial injections modulate bladder expression of NGF, TrkA, p75 and TRPV1 in patients with detrusor overactivity

How onabotulinumtoxinA (onab/A) injected in the detrusor muscle improves detrusor overactivity (DO) is still a matter of debate. Nerve growth factor (NGF) seems to play a role in determining urgency and DO. Recent studies showed that NGF decreases in patients with DO who respond to onab/A treatment. We investigated onab/A-induced changes on gene expression of NGF, TRPV1, TrkA and p75 in bladder wall tissue of patients affected by neurogenic and idiopathic DO. Twenty-five patients (18 with neurogenic DO and 7 with idiopathic DO) received onab/A injections into the detrusor muscle. Urodynamic studies and cystoscopies with sampling of the bladder wall were performed before and 1 month after onab/A injections. Onab/A-induced changes in urodynamic variables (first volume and maximum pressure of uninhibited detrusor contractions and maximum cystometric capacity) and NGF, TRPV1, TRKA, p75 gene expression by means of quantitative Real Time-Polymerase Chain Reaction. NGF protein levels were assessed in tissue homogenates by enzyme-linked immunosorbent assay. Onab/A significantly improved urodynamic findings (as shown by the increase in maximum cystometric capacity), decreased the bladder tissue levels of NGF protein and significantly increased NGF, TrkA, p75 and TRPV1 gene expression independently from the etiology of DO. No significant correlation has been found between NGF down-regulation and the increase in MCC. Correlations between NGF gene expression and NGF receptors' gene expression were influenced by onab/A dosages. In the short time follow-up, onab/A decreases NGF protein levels and increases NGF and associated receptors' gene expression possibly by inhibiting NGF release. Further studies with longer follow-up will clarify time course of onab/A-induced modifications in NGF expression.

Botulinum toxin injection for lower urinary tract dysfunction

Botulinum toxin has been recently accepted as a novel treatment for lower urinary tract dysfunctions refractory to conventional treatment. Review of the clinical trials in recent years, botulinum toxin type A has been widely used in the urethra or urinary bladder to treat voiding dysfunction due to detrusor sphincter dyssynergia, incontinence due to neurogenic or idiopathic detrusor overactivity, sensory disorders such as bladder hypersensitivity, overactive bladder, and interstitial cystitis/painful bladder syndrome. Intravesical botulinum toxin type A injection is effective in treatment of urinary incontinence due to detrusor overactivity in men and women, as well as in children. Currently botulinum toxin type A has also been applied to treat lower urinary tract symptoms due to benign prostatic hyperplasia in patients not suitable for surgery. This article reviewed the recent advances of botulinum toxin type A on lower urinary tract dysfunction.