Excitatory cholinergic and purinergic signaling in bladder are equally susceptible to botulinum neurotoxin a consistent with co-release of transmitters from efferent fibers

Assessing the Use of BotulinumtoxinA for Hyperactive Urinary Tract Dysfunction a Decade after Approval: A Single-Blind Study to Evaluate the Reduction in Pain in OnabotulinumtoxinA Detrusor Injection Using Different Injection Needles

Overactive bladder (OAB) has a significant impact on the quality of life; thus, it requires treatment that can be adhered to over a long period without undue side effects. The current treatment which uses an anticholinergic or β-3 agonist may fail to improve symptoms and has side effects, leading to high discontinuation rates. OnabotulinumtoxinA (OnabotA) detrusor injection has been approved for idiopathic OAB as a second-line treatment with good effectiveness and tolerability. This study used a visual analog scale (VAS) to assess the impact of the type of needle used for OnabotA detrusor injections under local anesthesia on the pain levels after each injection. This study included 68 female patients. We used three different needles with thicknesses ranging from 22 to 27 gauge, lengths between 4 and 5 mm, and different cuts. The sensation of pain was rated at each standardized injection location. Regardless of the needle used, the patients' perceptions of pain at the beginning of the procedure were rated as being less than the subsequent injections. Most pain sensations were rated as low to moderate. The mean pain sensation on the VAS was 2.5 ± 0.3 overall, i.e., for all patients and needles used. Statistically significant differences in pain sensation were rated only at some locations of the bladder (on the back wall and the right side of the bladder). The single needles averaged the following pain scores: 2.8 ± 0.3 for needle A (20 G, 4 mm), 2.1 ± 0.3 for needle B (27 G, 5 mm), and 2.6 ± 0.4 for needle C (20 G, 4 mm, sharp cut 15°). The 27-gauge needle caused significantly less pain, and it had no negative impact due to its length, which was 1 mm longer than the other needles. Thus, the needle thickness was a decisive factor in the patients' perceptions of pain.

Update on Overactive Bladder Therapeutic Options

BACKGROUND

Millions of Americans are burdened by overactive bladder (OAB) syndrome and the psychogenic and economic hardships that accompany it. Several theories attempt to explain OAB as a neurogenic dysfunction, myogenic dysfunction, urothelial dysfunction, or decreased expression of a channel protein secondary to bladder outlet obstruction. Given that the etiology of OAB is a working theory, the management of OAB is also an evolving subject matter in medicine. There are uncertainties surrounding the pathophysiology of OAB, the strength of a clinical diagnosis, and accurate reporting because of the disease's stigma and decreased use of health care.

DATA SOURCES

This is a narrative review that used PubMed, Google Scholar, Medline, and ScienceDirect to review literature on current and future OAB therapies.

RESULTS

Currently, first-line treatment for OAB is behavioral therapy that uses lifestyle modifications, bladder-control techniques, and psychotherapy. Second-line therapy includes antimuscarinic agents or beta 3 adrenergic agonists, and studies have shown that combination therapy with antimuscarinics and beta 3 adrenergic agonists provides even greater efficacy than monotherapy. Third-line therapies discussed include onabotulinumtoxinA, posterior tibial nerve stimulation, and sacral neuromodulation. OnabotulinumtoxinA has been FDA-approved as a nonpharmaceutical treatment option for refractory OAB with minimal side effects restricted to the urinary tract. Posterior tibial nerve modulation and sacral neuromodulation are successful in treating refractory OAB, but the costs and complication rates make them high-risk procedures. Therefore, surgical intervention should be a last resort. Estrogen therapy is effective in alleviating urinary incontinence in postmenopausal women, consistent with the association between estrogen deficiency and genitourinary syndrome. Potassium channel activators, voltage-gated calcium channel blockers, and phosphodiesterase inhibitors look to be promising options for the future of OAB management. As new therapies are developed, individuals with OAB can better personalize their treatment to maximize their quality of life and cost-effective care.

The clinical application of intravesical botulinum toxin A injection in patients with overactive bladder and interstitial cystitis

Botulinum toxin A (BoNT-A) has been widely used in several urological functional disorders including neurogenic detrusor overactivity (NDO), overactive bladder (OAB), lower urinary tract dysfunction, and interstitial cystitis/bladder pain syndrome (IC/BPS). Chronic inflammation is found in a large proportion of patients with OAB and IC/BPS. The chronic inflammation activates sensory afferents which resulting in central sensitization and bladder storage symptoms. Because BoNT-A can inhibit the sensory peptides released from the vesicles in sensory nerve terminals, the inflammation can be reduced and symptom subsided. Previous studies have demonstrated that the quality of life improved after BoNT-A injections, both in neurogenic and non-NDO. Although the use of BoNT-A in treatment of IC/BPS has not been approved by FDA, intravesical BoNT-A injection has been included in the AUA guideline as the fourth line therapy. Generally, intravesical injections of BoNT-A are well tolerated, though transient hematuria and urinary tract infection can occur after the procedure. In order to prevent these adverse events, experimental trials have been conducted to test if BoNT-A can be delivered into the bladder wall without intravesical injection under anesthesia such as using liposomes encapsulated BoNT-A or application of low energy shock wave on the bladder to facilitate BoNT-A penetrating across the urothelium and treat OAB or IC/BPS. This article reviews current clinical and basic researches of BoNT-A on OAB and IC/BPS.

Hengli® Chinese Botulinum Toxin Type A for Treatment of Patients With Overactive Bladder: A Multicenter, Prospective, Randomized, Double-Blind, Placebo-Controlled Trial

Objective: To evaluate the efficacy and safety of Hengli® Chinese botulinum toxin type A (BTX-A; 100 U) in Chinese patients with overactive bladder. Methods: This study was a multicenter, randomized, double-blind, placebo-controlled trial in Chinese patients who were inadequately managed with anticholinergic medications. Eligible patients were randomized 2:1 to receive intradetrusor injections of Hengli® BTX-A (n = 144) or placebo (n = 72). The primary endpoint was the change in the number of daily micturition episodes at week 6 from baseline. The secondary efficacy endpoints included the average frequency of urgency and urinary incontinence (UI) episodes per day, urgency score, average micturition volume per day, OABSS, and QoL score. Results: In the Hengli® BTX-A group, there was a significantly greater reduction in the average number of micturition episodes per 24 h compared with the placebo group (3.28 vs. 1.43; p = 0.003). Moreover, there was a significantly greater improvement in the daily number of urgency episodes, micturition volume and OABSS score. An increased post-void residual urine volume, dysuria, and urinary tract infection represented adverse events (AEs) in the Hengli® BTX-A group. Most AEs were mild or moderate in severity. One patient in the BTX-A group initiated clean intermittent catheterization (CIC) during treatment. Conclusion: Hengli® BTX-A treatment was well-tolerated and resulted in significant improvements in OAB symptoms among Chinese patients inadequately managed by anticholinergics. Clinical Trial Registration: http://www.chinadrugtrials.org.cn/clinicaltrials.prosearch.dhtml, Identifier: CTR20131190.

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.

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.

Knockin mouse models demonstrate differential contributions of synaptotagmin-1 and -2 as receptors for botulinum neurotoxins

Botulinum neurotoxins (BoNTs) are the most potent toxins known and are also utilized to treat a wide range of disorders including muscle spasm, overactive bladder, and pain. BoNTs' ability to target neurons determines their specificity, potency, and therapeutic efficacy. Homologous synaptic vesicle membrane proteins synaptotagmin-1 (Syt1) and synaptotagmin-2 (Syt2) have been identified as receptors for BoNT family members including BoNT/B, DC, and G, but their contributions at physiologically relevant toxin concentrations in vivo have yet to be validated and established. Here we generated two knockin mutant mouse models containing three designed point-mutations that specifically disrupt BoNT binding in endogenous Syt1 or Syt2, respectively. Utilizing digit abduction score assay by injecting toxins into the leg muscle, we found that Syt1 mutant mice showed similar sensitivity as the wild type mice, whereas Syt2 mutant mice showed reduced sensitivity to BoNT/B, DC, and G, demonstrating that Syt2 is the dominant receptor at skeletal neuromuscular junctions. We further developed an in vivo bladder injection assay for analyzing BoNT action on bladder tissues and demonstrated that Syt1 is the dominant toxin receptor in autonomic nerves controlling bladder tissues. These findings establish the critical role of protein receptors for the potency and specificity of BoNTs in vivo and demonstrate the differential contributions of Syt1 and Syt2 in two sets of clinically relevant target tissues.

P2X3-Containing Receptors as Targets for the Treatment of Chronic Pain

Current therapies for the treatment of chronic pain provide inadequate relief for millions of suffering patients, demonstrating the need for better therapies that will treat pain effectively and improve the quality of patient's lives. Better understanding of the mechanisms that mediate chronic pain is critical for developing drugs with improved clinical outcomes. Adenosine triphosphate (ATP) is a key modulator in nociceptive pathways. Release of ATP from injured tissue or sympathetic efferents has sensitizing effects on sensory neurons in the periphery, and presynaptic vesicular release of ATP from the central terminals can increase glutamate release thereby potentiating downstream central sensitization mechanisms, a condition thought to underlie many chronic pain conditions. The purinergic receptors on sensory nerves primarily responsible for ATP signaling are P2X3 and P2X2/3. Selective knockdown experiments, or inhibition with small molecules, demonstrate P2X3-containing receptors are key targets to modulate nociceptive signals. Preclinical studies have identified that P2X3-containing receptors are critical for sensory transduction for bladder function, and clinical studies have shown promise in treatment for bladder pain and pain associated with osteoarthritis. Further clinical characterization of antagonists to P2X3-containing receptors may lead to improved therapies in the treatment of chronic pain.

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.

Neuronal selectivity of botulinum neurotoxins

Botulinum neurotoxins (BoNTs) are highly potent toxins responsible for a severe disease, called botulism. They are also efficient therapeutic tools with an increasing number of indications ranging from neuromuscular dysfunction to hypersecretion syndrome, pain release, depression as well as cosmetic application. BoNTs are known to mainly target the motor-neurons terminals and to induce flaccid paralysis. BoNTs recognize a specific double receptor on neuronal cells consisting of gangliosides and synaptic vesicle protein, SV2 or synaptotagmin. Using cultured neuronal cells, BoNTs have been established blocking the release of a wide variety of neurotransmitters. However, BoNTs are more potent in motor-neurons than in the other neuronal cell types. In in vivo models, BoNT/A impairs the cholinergic neuronal transmission at the motor-neurons but also at neurons controlling secretions and smooth muscle neurons, and blocks several neuronal pathways including excitatory, inhibitory, and sensitive neurons. However, only a few reports investigated the neuronal selectivity of BoNTs in vivo. In the intestinal wall, BoNT/A and BoNT/B target mainly the cholinergic neurons and to a lower extent the other non-cholinergic neurons including serotonergic, glutamatergic, GABAergic, and VIP-neurons. The in vivo effects induced by BoNTs on the non-cholinergic neurons remain to be precisely investigated. We report here a literature review of the neuronal selectivity of BoNTs.

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

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

Outcomes of Intradetrusor Onabotulinum Toxin A Therapy in Overactive Bladder Refractory to Sacral Neuromodulation

Purpose

Intradetrusor onabotulinum toxin A (BTXA) and sacral neuromodulation (SNM) are effective third-line therapies for overactive bladder (OAB). We aimed to measure the outcomes of BTXA for treatment of OAB refractory to initial SNM and identify patient characteristics associated with these outcomes.

Methods

This retrospective cohort study included patients who failed to respond to initial SNM treatment for OAB and subsequently received BTXA at a single provider’s clinic between January 2013 and December 2016. Treatment successes were defined as patients willing to continue BTXA or who found symptom relief whereas treatment failures discontinued BTXA due to adverse effects or lack of symptom relief. Symptoms and patient-reported outcomes on validated questionnaires were compared before the initial BTXA trial to 2 months after the last BTXA treatment. The SNM failure BTXA groups were also compared to BTXA SNM naïve groups.

Results

Of 18 patients who received BTXA after failed SNM treatment, 7 (39%) achieved treatment success. Successfully treated patients demonstrated decreased urinary frequency from a median 11 voids/day pre-BTXA to 8 voids/day with BTXA (P=0.042). Patients whose treatment failed reported increased complaints of a weak urinary stream (P=0.03) and higher frequency of straining to urinate (P=0.016) than the successful treatment group pre-BTXA. Compared to BTXA patients without prior SNM, the odds of failing BTXA after initial SNM were 3.6 times higher (P=0.016).

Conclusions

BTXA appears effective for OAB refractory to SNM, although the success rate is lower compared to BTXA patients without SNM exposure.

β3-Adrenoceptor agonists inhibit purinergic receptor-mediated contractions of the murine detrusor

β₃-Adrenoceptor (β₃-AR) agonists are used to treat overactive bladder syndrome; however, their mechanism of action has not been determined. The aims of this study were to compare the effects of β₃-AR agonists on cholinergic versus purinergic receptor-mediated contractions of the detrusor and to examine the mechanisms underlying inhibition of the purinergic responses by β₃-AR agonists. Isometric tension recordings were made from strips of murine detrusor and whole cell current recordings were made from freshly isolated detrusor myocytes using the patch-clamp technique. Transcriptional expression of exchange protein directly activated by cAMP (EPAC) subtypes in detrusor strips was assessed using RT-PCR and real-time quantitative PCR. The β₃-AR agonists BRL37344 and CL316243 (100 nM) inhibited cholinergic nerve-mediated contractions of the detrusor by 19 and 23%, respectively, but did not reduce contractions induced by the cholinergic agonist carbachol (300 nM). In contrast, BRL37344 and CL316243 inhibited purinergic nerve-mediated responses by 55 and 56%, respectively, and decreased the amplitude of contractions induced by the P2X receptor agonist α,β-methylene ATP by 40 and 45%, respectively. The adenylate cyclase activator forskolin inhibited purinergic responses, and these effects were mimicked by a combination of the PKA activator N⁶-monobutyryl-cAMP and the EPAC activator 8-pCPT-2'-O-methyl-cAMP-AM (007-AM). Application of ATP (1 μM) evoked reproducible P2X currents in isolated detrusor myocytes voltage-clamped at -60 mV. These responses were reduced in amplitude in the presence of BRL37344 and also by 007-AM. This study demonstrates that β₃-AR agonists reduce postjunctional purinergic responses in the detrusor via a pathway involving activation of the cAMP effector EPAC.

Effect of pregnancy on the cholinergic responses of the bladder: role of acetylcholinesterase

OBJECTIVES

Pregnancy is associated with many functional changes of the urinary bladder. It was reported that most of healthy women complain from urinary symptoms during pregnancy. The parasympathetic system is mainly mediating bladder emptying. The aim of the study is to investigate the cholinergic effect and the role of acetylcholinesterase in the bladder during pregnancy.

METHODS

Sixteen rats were used in the present study as control group (non-pregnant) and pregnant group (18-20 days pregnant). Isolated urinary smooth muscle strips were suspended in organ baths filled with Krebs' solution for isometric tension recording.

RESULTS

Electric field stimulation (EFS), (0.1-40 Hz), of the control and pregnant bladder preparations produced frequency-dependent contractions. Atropine (1 µM) inhibited EFS-induced contractions in the two groups by 65% and 50% respectively indicating the response of cholinergic innervation. Neostigmine significantly enhanced EFS responses, confirming its selectivity for inhibiting acetylcholinesterase which is responsible for termination of acetylcholine. Concentration-response curves for acetylcholine were reduced in pregnant group than control. Concentration-response curves for ATP were increased in pregnant group than control. Neostigmine augmented concentration-response curves for acetylcholine in control and pregnant groups. The effect of neostigmine on acetylcholine contractile responses in pregnancy group was higher than in control.

CONCLUSIONS

Urinary bladder dysfunction during pregnancy might be due to augmentation of acetylcholinesterase effect. This will lead to the decrease in response to cholinergic stimuli. New pharmaceutical drugs specifically affecting the enzyme in the bladder can help in avoiding the unpleasant urinary symptoms during pregnancy.

BDNF overexpression in the bladder induces neuronal changes to mediate bladder overactivity

Elevated levels of brain-derived neurotrophic factor (BDNF) in urine of overactive bladder (OAB) patients support the association of BDNF with OAB symptoms, but the causality is not known. Here, we investigated the functionality of BDNF overexpression in rat bladder following bladder wall transfection of either BDNF or luciferase (luciferase) transgenes (10 µg). One week after transfection, BDNF overexpression in bladder tissue and elevation of urine BDNF levels were observed together with increased transcript of BDNF, its cognate receptors (TrkB and p75^NTR), and downstream PLCγ isoforms in bladder. BDNF overexpression can induce the bladder overactivity (BO) phenotype which is demonstrated by the increased voiding pressure and reduced intercontractile interval during transurethral open cystometry under urethane anesthesia. A role for BDNF-mediated enhancement of prejunctional cholinergic transmission in BO is supported by the significant increase in the atropine- and neostigmine-sensitive component of nerve-evoked contractions and upregulation of choline acetyltransferase, vesicular acetylcholine transporter, and transporter Oct2 and -α1 receptors. In addition, higher expression of transient receptor channels (TRPV1 and TRPA1) and pannexin-1 channels in conjunction with elevation of ATP and neurotrophins in bladder and also in L6/S1 dorsal root ganglia together support a role for sensitized afferent nerve terminals in BO. Overall, genomic changes in efferent and afferent neurons of bladder induced by the overexpression of BDNF per se establish a mechanistic link between elevated BDNF levels in urine and dysfunctional voiding observed in animal models and in OAB patients.

Augmentation of VAMP-catalytic activity of botulinum neurotoxin serotype B does not result in increased potency in physiological systems

Botulinum neurotoxins (BoNTs) are used extensively as therapeutic agents. Serotypes A and B are available as marketed products. Higher doses of BoNT/B are required to reach an efficacy similar to that of products containing BoNT/A. Advances in our understanding of BoNT/B mechanism of action have afforded the opportunity to make rational modifications to the toxin aimed at increasing its activity. Recently, a mutation in the light chain of BoNT/B (S201P) was described that increases the catalytic activity of the isolated BoNT/B light chain in biochemical assays. In this study, we have produced two full-length recombinant BoNT/B toxins in E.coli-one wild type (rBoNT/B1) and one incorporating the S201P mutation (rBoNT/B1(S201P)). We have compared the activity of these two molecules along with a native BoNT/B1 in biochemical cell-free assays and in several biological systems. In the cell-free assay, which measured light-chain activity alone, rBoNT/B1(S201P) cleaved VAMP-2 and VAMP-1 substrate with an activity 3-4-fold higher than rBoNT/B1. However, despite the enhanced catalytic activity of rBoNT/B1(S201P), there was no significant difference in potency between the two molecules in any of the in vitro cell-based assays, using either rodent spinal cord neurons or cortical neurons. Similarly in ex vivo tissue preparations rBoNT/B1(S201P) was not significantly more potent than rBoNT/B1 at inhibiting either diaphragm or detrusor (bladder) muscle activity in C57BL/6N and CD1 mice. Finally, no differences between rBoNT/B1 and rBoNT/B1(S201P) were observed in an in vivo digit abduction score (DAS) assay in C57BL/6N mice, either in efficacy or safety parameters. The lack of translation from the enhanced BoNT/B1(S201P) catalytic activity to potency in complex biological systems suggests that the catalytic step is not the rate-limiting factor for BoNT/B to reach maximum efficacy. In order to augment the efficacy of BoNT/B in humans, strategies other than enhancing light chain activity may need to be considered.

A novel therapeutic with two SNAP-25 inactivating proteases shows long-lasting anti-hyperalgesic activity in a rat model of neuropathic pain

A pressing need exists for long-acting, non-addictive medicines to treat chronic pain, a major societal burden. Botulinum neurotoxin type A (BoNT/A) complex - a potent, specific and prolonged inhibitor of neuro-exocytosis - gives some relief in several pain disorders, but not for all patients. Our study objective was to modify BoNT/A to overcome its inability to block transmitter release elicited by high [Ca²⁺]_i and increase its limited analgesic effects. This was achieved by fusing a BoNT/A gene to that for the light chain (LC) of type/E. The resultant purified protein, LC/E-BoNT/A, entered cultured sensory neurons and, unlike BoNT/A, inhibited release of calcitonin gene-related peptide evoked by capsaicin. Western blotting revealed that this improvement could be due to a more extensive truncation by LC/E of synaptosomal-associated protein of Mr = 25 k, essential for neuro-exocytosis. When tested in a rat spared nerve injury (SNI) model, a single intra-plantar (IPL) injection of LC/E-BoNT/A alleviated for ∼2 weeks mechanical and cold hyper-sensitivities, in a dose-dependent manner. The highest non-paralytic dose (75 U/Kg, IPL) proved significantly more efficacious than BoNT/A (15 U/Kg, IPL) or repeated systemic pregabalin (10 mg/Kg, intraperitoneal), a clinically-used pain modulator. Effects of repeated or delayed injections of this fusion protein highlighted its analgesic potential. Attenuation of mechanical hyperalgesia was extended by a second administration when the effect of the first had diminished. When injected 5 weeks after injury, LC/E-BoNT/A also reversed fully-established mechanical and cold hyper-sensitivity. Thus, combining advantageous features of BoNT/E and/A yields an efficacious, locally-applied and long-acting anti-hyperalgesic.

Botulinum Neurotoxins Serotypes A and B induce paralysis of mouse striated and smooth muscles with different potencies

To address the scarcity of direct comparison of botulinum neurotoxin serotypes activity on smooth versus striatal muscle, we have studied the action of BoNT/A1 and BoNT/B1 on ex vivo preparations of both muscle types. We have set up and characterized a model of neurogenic contractions in the isolated mouse bladder, and used this model to explore the effects of the two serotypes on contractions evoked by electrical field stimulation. Both toxins were also tested in the mouse phrenic nerve hemidiaphragm assay, to compare their potency in smooth versus striated muscle. The characterization of the model of neurogenic contractions in the isolated mouse bladder indicates that about half of the activity is driven by purinergic signaling, and about half by cholinergic signaling. Furthermore, we find that BoNT/B1 is more potent than BoNT/A1 in inhibiting activity in the mouse detrusor smooth muscle preparation, but that both toxins have comparable potency on the striated muscle activity of the phrenic nerve hemidiaphragm model. We also show that these findings are mouse strain independent. In conclusion, the established mouse bladder detrusor smooth muscle model is able to discriminate between different botulinum neurotoxin serotypes and could be a useful preclinical tool to explore the pathophysiology of bladder overactivity, as well as the effects of new therapeutic candidates. It is interesting to note that the high proportion of purinergic transmission driving detrusor contractions in this model is similar to that seen in neurodetrusor overactivity disease, making this model relevant with regard to pathophysiological interest.

Short- and long-term (trophic) purinergic signalling

There is long-term (trophic) purinergic signalling involving cell proliferation, differentiation, motility and death in the development and regeneration of most systems of the body, in addition to fast purinergic signalling in neurotransmission, neuromodulation and secretion. It is not always easy to distinguish between short- and long-term signalling. For example, adenosine triphosphate (ATP) can sometimes act as a short-term trigger for long-term trophic events that become evident days or even weeks after the original challenge. Examples of short-term purinergic signalling during sympathetic, parasympathetic and enteric neuromuscular transmission and in synaptic transmission in ganglia and in the central nervous system are described, as well as in neuromodulation and secretion. Long-term trophic signalling is described in the immune/defence system, stratified epithelia in visceral organs and skin, embryological development, bone formation and resorption and in cancer. It is likely that the increase in intracellular Ca(2+) in response to both P2X and P2Y purinoceptor activation participates in many short- and long-term physiological effects.This article is part of the themed issue 'Evolution brings Ca(2+) and ATP together to control life and death'.

Botulinum Toxin A and Lower Urinary Tract Dysfunction: Pathophysiology and Mechanisms of Action

The use of onabotulinumtoxinA (BoNT-A) for the treatment of lower urinary tract diseases (LUTD) has increased markedly in recent years. The indications for BoNT-A treatment of LUTD now include neurogenic or idiopathic detrusor overactivity, interstitial cystitis/bladder pain syndrome and voiding dysfunction. The mechanisms of BoNT-A action on LUTDs affect many different aspects. Traditionally, the effects of BoNT-A were believed to be attributable to inhibition of acetylcholine release from the presynaptic efferent nerves at the neuromuscular junctions in the detrusor or urethral sphincter. BoNT-A injection in the bladder also regulated sensory nerve function by blocking neurotransmitter release and reducing receptor expression in the urothelium. In addition, recent studies revealed an anti-inflammatory effect for BoNT-A. Substance P and nerve growth factor in the urine and bladder tissue decreased after BoNT-A injection. Mast cell activation in the bladder also decreased. BoNT-A-induced improvement of urothelium function plays an important mitigating role in bladder dysfunction. Vascular endothelial growth factor expression in urothelium decreased after BoNT-A injection, as did apoptosis. Studies also revealed increased apoptosis in the prostate after BoNT-A injection. Although BoNT-A injection has been widely used to treat different LUTDs refractory to conventional treatment, currently, onabotulinumtoxinA has been proven effective only on urinary incontinence due to IDO and NDO in several large-scale clinical trials. The effects of onabotulinumtoxinA on other LUTDs such as interstitial cystitis, benign prostatic hyperplasia, dysfunctional voiding or detrusor sphincter dyssynergia have not been well demonstrated.

A1 Adenosine Receptor-Mediated Inhibition of Parasympathetic Neuromuscular Transmission in Human and Murine Urinary Bladder

The potential role of A1 adenosine receptors in modulating neuromuscular transmission in the detrusor muscle of the urinary bladder has been tested in human and murine preparations with the intent to determine the viability of using adenosine receptor agonists as adjuncts to treat overactive bladder. In human detrusor muscle preparations, contractile responses to electrical field stimulation were inhibited by the selective A1 adenosine receptor agonists 2-chloro-N(6)-cyclopentyladenosine, N(6)-cyclopentyladenosine (CPA), and adenosine (rank order of potency: 2-chloro-N(6)-cyclopentyladenosine > CPA > adenosine). Pretreatment with 8-cyclopentyl-3-[3-[[4(fluorosulphonyl)benzoyl]oxy]propyl]-1-propylxanthine, an irreversible A1 antagonist, blocked the effects of CPA, thus confirming the role of A1 receptors in human detrusor preparations. In murine detrusor muscle preparations, contractions evoked by electrical field stimulation were reduced by CPA or adenosine. Amplitudes of the P2X purinoceptor-mediated excitatory junctional potentials (EJPs) recorded with intracellular microelectrodes were reduced in amplitude by CPA and adenosine with no effect on the spontaneous EJP amplitudes, confirming the prejunctional action of these agents. 8-Cyclopentyltheophylline, a selective A1 receptor antagonist, reversed the effects of CPA on EJP amplitudes with no effect of spontaneous EJPs, confirming the role of A1 receptors in mediating these effects.

Botulinum neurotoxin: Progress in negating its neurotoxicity; and in extending its therapeutic utility via molecular engineering. MiniReview

While the poisonous effects of botulinum neurotoxin (BoNT) have been recognized since antiquity, the overall actions and mechanisms of effects of BoNT have been elucidated primarily over the past several decades. The general utility of BoNT is described in the paper, but the focus is mainly on the approaches towards negating the toxic effects of BoNT, and on the projection of an engineered BoNT molecule serving as a Trojan Horse to deliver a therapeutic load for treatment of a host of medical disorders. The BoNT molecule is configured with a binding domain, a zinc-dependent protease with specificity primarily for vesicular proteins, and a translocation domain for delivery of the metalloprotease into the cytoplasm. The anti-toxin approaches for BoNT include the use of vaccines, antibodies, block of BoNT binding or translocation, inhibition of metalloprotease activity, impeded translocation of the protease/catalytic domain, and inhibition of the downstream Src signaling pathway. Projections of BoNT as a therapeutic include its targeting to non-cholinergic nerves, also targeting to non-neuronal cells for treatment of hypersecretory disorders (e.g., cystic fibrosis), and treatment of hormonal disorders (e.g., acromegaly). Still in the exploratory phase, there is the expectation of major advances in BoNT neuroprotective strategies and burgeoning utility of engineered BoNTs as therapeutics.

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.

Presence of Cleaved Synaptosomal-Associated Protein-25 and Decrease of Purinergic Receptors P2X3 in the Bladder Urothelium Influence Efficacy of Botulinum Toxin Treatment for Overactive Bladder Syndrome

OBJECTIVES

To evaluate whether botulinum toxin A (BoNT-A) injection and Lipotoxin (liposomes with 200 U of BoNT-A) instillation target different proteins, including P2X3, synaptic vesicle glycoprotein 2A, and SNAP-25, in the bladder mucosa, leading to different treatment outcomes.

MATERIALS AND METHODS

This was a retrospective study performed in a tertiary teaching hospital. We evaluated the clinical results of 27 OAB patients treated with intravesical BoNT-A injection (n = 16) or Lipotoxin instillation (n = 11). Seven controls were treated with saline. Patients were injected with 100 U of BoNT-A or Lipotoxinin a single intravesical instillation. The patients enrolled in this study all had bladder biopsies performed at baseline and one month after BoNT-A therapy. Treatment outcome was measured by the decreases in urgency and frequency episodes at 1 month. The functional protein expressions in the urothelium were measured at baseline and after 1 month. The Wilcoxon signed-rank test and ordinal logistic regression were used to compare the treatment outcomes.

RESULTS

Both BoNT-A injection and Lipotoxin instillation treatments effectively decreased the frequency of urgency episodes in OAB patients. Lipotoxin instillation did not increase post-void residual volume. BoNT-A injection effectively cleaved SNAP-25 (p < 0.01). Liposome encapsulated BoNT-A decreased urothelial P2X3 expression in the five responders (p = 0.04), while SNAP-25 was not significantly cleaved.

CONCLUSIONS

The results of this study provide a possible mechanism for the therapeutic effects of BoNT-A for the treatment of OAB via different treatment forms. BoNT-A and Lipotoxin treatments effectively decreased the frequency of urgency episodes in patients with OAB.

Treatment of Chronic Migraine with Focus on Botulinum Neurotoxins

Migraine is the most common neurological disorder, and contributes to disability and large healthcare costs in the United States and the world. The treatment of migraine until recently has focused on medications, both abortive and prophylactic, but treatment of chronic migraine has been revolutionized with the introduction of botulinum toxin injection therapy. In this review, we explore the current understanding of migraine pathophysiology, and the evolution of the use of botulinum toxin therapy including proposed pathophysiological mechanisms through animal data. We also discuss the similarities and differences between three injection techniques.

Preclinical assessment of potential interactions between botulinum toxin and neuromodulation for bladder micturition reflex

BACKGROUND

While botulinum toxin A (BoNT-A) has become a more commonly used second-line treatment for patients with detrusor overactivity, it remains unknown whether the impacts of this therapy may persist to influence other therapies such as sacral neuromodulation. In this preclinical study we have evaluated urodynamic functions to intradetrusor injection of BoNT-A and the bladder inhibitory effects of spinal nerve stimulation (SNS) following BoNT-A treatment.

METHODS

Female rats were anesthetized with 3 % isoflurane. BoNT-A (2 units, 0.2 ml) or saline were injected into the detrusor. Rats then were housed for 2 days to 1 month before neuromodulation study. Monopolar electrodes were placed under each of the L6 spinal nerve bilaterally under urethane anesthesia. A bladder cannula was inserted via the urethra for saline infusion and intravesical pressure recording.

RESULTS

Intradetrusor injection of BoNT-A for 1-2 weeks or 1 month significantly increased bladder capacity compared with saline injection (p < 0.05, two-way ANOVA). Following BoNT-A, SNS attenuated the frequency of bladder contractions, either eliminating bladder contractions or reducing the contraction frequency during electrical stimulation. Inhibition of the contraction frequency by SNS following BoNT-A treated rats was not different from that measured following saline injection.

CONCLUSIONS

BoNT-A increased the bladder capacity, but compensating for additional saline infusion to the enlarged urinary bladder in BoNT-A pretreated rats, the bladder contractions induced by bladder filling were attenuated by SNS. BoNT-A did not alter the ability of SNS to inhibit bladder contraction following intradetrusor injection of BoNT-A for 2 days, 1-2 weeks or 1 month. These results support further pre-clinical and clinical studies to evaluate potential interactions or combination therapy with neuromodulation and intradetrusor BoNT-A therapeutic approaches.

Chapter 3: Molecular basis for the therapeutic effectiveness of botulinum neurotoxin type A

The utility of botulinum neurotoxin type A (BoNT/A) for treating overactive muscles and endocrine glands is attributable to a unique conflation of properties honed to exploit and inactivate synaptic transmission. Specific, high-affinity coincident binding to gangliosides plus an intraluminal loop of synaptic vesicle protein 2 (SV2) by the heavy chain (HC) of BoNT/A confers selectivity for presynaptic nerve terminals and subsequent uptake by endocytosis. Upon vesicle acidification, the HC forms a channel for transmembrane transfer of the light chain to the cytosol, as observed by single channel recordings. The light chain is a Zn(2+) -dependent endoprotease that cleaves and inactivates SNAP-25, thereby blocking exocytotic release of transmitters, a discovery that revealed the pivotal role of the latter in synaptic vesicle fusion. A di-leucine motif in BoNT/A light chain stabilizes this protease, contributing to its longevity inside nerves. The ubiquity of SV2 and SNAP-25 has prompted re-evaluation of the nerve types susceptible to BoNT/A. In urology, there is emerging evidence that BoNT/A blocks neuropeptide release from afferent nerves, exocytosis of acetylcholine and purines from efferent nerves, and possibly ATP release from the urothelium. Suppression by BoNT/A of the surface expression of nociceptor channels on bladder afferents might also contribute to its improvement of urological sensory symptoms.

The pharmacological rationale for combining muscarinic receptor antagonists and β-adrenoceptor agonists in the treatment of airway and bladder disease

•

Muscarinic receptors increase smooth muscle tone in airways and urinary bladder.

•

β-Adrenoceptors relax smooth muscle tone and oppose muscarinic contraction.

•

Opposition involves transmitter release, signal transduction and receptor expression.

•

This supports the combined use of muscarinic antagonists and β-adrenoceptor agonists.

Muscarinic receptor antagonists and β-adrenoceptor agonists are used in the treatment of obstructive airway disease and overactive bladder syndrome. Here we review the pharmacological rationale for their combination. Muscarinic receptors and β-adrenoceptors are physiological antagonists for smooth muscle tone in airways and bladder. Muscarinic agonism may attenuate β-adrenoceptor-mediated relaxation more than other contractile stimuli. Chronic treatment with one drug class may regulate expression of the target receptor but also that of the opposing receptor. Prejunctional β₂-adrenoceptors can enhance neuronal acetylcholine release. Moreover, at least in the airways, muscarinic receptors and β-adrenoceptors are expressed in different locations, indicating that only a combined modulation of both systems may cause dilatation along the entire bronchial tree. While all of these factors contribute to a rationale for a combination of muscarinic receptor antagonists and β-adrenoceptor agonists, the full value of such combination as compared to monotherapy can only be determined in clinical studies.

Purinergic signalling in the urinary tract in health and disease

Purinergic signalling is involved in a number of physiological and pathophysiological activities in the lower urinary tract. In the bladder of laboratory animals there is parasympathetic excitatory cotransmission with the purinergic and cholinergic components being approximately equal, acting via P2X1 and muscarinic receptors, respectively. Purinergic mechanosensory transduction occurs where ATP, released from urothelial cells during distension of bladder and ureter, acts on P2X3 and P2X2/3 receptors on suburothelial sensory nerves to initiate the voiding reflex, via low threshold fibres, and nociception, via high threshold fibres. In human bladder the purinergic component of parasympathetic cotransmission is less than 3 %, but in pathological conditions, such as interstitial cystitis, obstructed and neuropathic bladder, the purinergic component is increased to 40 %. Other pathological conditions of the bladder have been shown to involve purinoceptor-mediated activities, including multiple sclerosis, ischaemia, diabetes, cancer and bacterial infections. In the ureter, P2X7 receptors have been implicated in inflammation and fibrosis. Purinergic therapeutic strategies are being explored that hopefully will be developed and bring benefit and relief to many patients with urinary tract disorders.

Botulinum toxin A detrusor injections reduce postsynaptic muscular M2, M3, P2X2, and P2X3 receptors in children and adolescents who have neurogenic detrusor overactivity: a single-blind study

OBJECTIVE

To analyze the effect of OnabotulinumtoxinA detrusor injections on postsynaptic muscular receptors in children and adolescents with neurogenic detrusor overactivity.

MATERIALS AND METHODS

A bladder augmentation became necessary in 10 children and adolescents (7 males, 3 females; median age, 12 years) who had neurogenic detrusor overactivity. Seven had previously received 1 to 8 (average 3.86) OnabotulinumtoxinA detrusor injections, but their detrusor pressure could not be maintained at tolerable levels because of low-compliance bladder. The last injection session had been completed an average of 3 months (range, 1.5-3.5 months) previously. Three patients had never received that therapy and were considered controls. On the bladder dome resections, a specific receptor analysis (muscarinic M2 and M3 and purinergic P2X1, P2X2, and P2X3) was performed with confocal immunofluorescence, and nerve fiber density was analyzed with light-microscopic 3,3'-diaminobenzidine-immunohistochemical staining.

RESULTS

Receptor analysis showed a downregulation of all examined receptors after OnabotulinumtoxinA injections; the reductions in M2, M3, P2X2, and P2X3 receptors reached a significance level of P <.05 (Mann-Whitney test). The ratios of means (OnabotulinumtoxinA-to-control) were 0.26 for M2, 0.33 for M3, 0.35 for P2X1, 0.19 for P2X2, and 0.37 for P2X3.

CONCLUSION

OnabotulinumtoxinA detrusor injections led to significant reductions in muscular M2, M3, P2X2, and P2X3 receptors. The reductions probably affect the generated force in the urinary bladder and could contribute to the clinically observed increase in residual urine.

Alterations in peripheral purinergic and muscarinic signaling of rat bladder after long-term fructose-induced metabolic syndrome

PURPOSE

We explored the pathophysiologic mechanisms of long-term fructose-induced lower urinary tract symptoms (LUTS) in rats.

METHODS

Male Wistar rats were fed with fructose for 3 or 6 months. Biochemical and transcystometric parameters were compared between fructose-fed and age-matched normal-diet rats. Pelvic nerve and external urethral sphincter-electromyogram activity recordings were performed to investigate fructose effects on neural control of bladders. Mitochondrial structure, ATP and acetylcholine content and purinergic and muscarinic cholinergic receptors were examined. Cytosolic cytochrome C staining by Western blot and immunocytochemistry for mitochondrial injury and PGP 9.5 stain for nerve density were also determined.

RESULTS

The fructose-fed rats with higher plasma triglyceride, LDL and fasting glucose levels displayed LUTS with increased frequency and suppressed voiding contractile amplitude in phase 1 and phase 2 duration versus normal-diet control. Fructose feeding altered the firing types in pelvic afferent and efferent nerves and external urethral sphincter-electromyogram activity. Increased mast cell number, disrupted and swollen mitochondria, increased cytosolic cytochrome C stain and expression and decreased nerve density in bladder smooth muscle layers appeared in the fructose-fed rats. Fructose feeding also significantly reduced ATP and acetylcholine content and enhanced protein expression of postsynaptic P(2)X(1), P(2)X(2) and P(2)X(3) purinergic receptors and M(2) and M(3) muscarinic cholinergic receptors expression in the smooth muscles of urinary bladder.

CONCLUSION

Long-term fructose feeding induced neuropathy and myopathy in the urinary bladders. Impaired mitochondrial integrity, reduced nerve density, ATP and acetylcholine content and upregulation of purinergic and muscarinic cholinergic receptors expression may contribute to the bladder dysfunction of fructose-fed animals.

Purinergic signalling in the lower urinary tract

The aim of this review is to describe the conceptual steps contributing to our current knowledge of purinergic signalling and to consider its involvement in the physiology and pathophysiology of the lower urinary tract. The voiding reflex involves ATP released as a cotransmitter with acetylcholine from parasympathetic nerves supplying the bladder and ATP released from urothelial cells during bladder distension to initiate the voiding reflex via P2X3 receptors on suburothelial low threshold sensory nerve fibres. This mechanosensory transduction pathway also participates, via high threshold sensory nerve fibres, in the initiation of pain in bladder and ureter. Treatment of prostate and bladder cancer with ATP is effective against the primary tumours in animal models and human cell lines, via P2X5 and P2X7 receptors, and also improves the systemic symptoms associated with advanced malignancy. Acupuncture is widely used for the treatment of urinary disorders, and a purinergic hypothesis is discussed for the underlying mechanism.

Differential effects of botulinum neurotoxin A on bladder contractile responses to activation of efferent nerves, smooth muscles and afferent nerves in rats

PURPOSE

To determine the mechanisms of botulinum neurotoxin A (Metabiologics, Madison, Wisconsin) induced inhibition of bladder activity we examined the effect of botulinum neurotoxin A on detrusor contractile responses to the activation of L-type voltage-gated Ca(2+) channels, and efferent and afferent nerve terminals in the rat bladder.

MATERIALS AND METHODS

Rat bladder strips were incubated for 3 hours with different concentrations of botulinum neurotoxin A (0.3 to 100 nM). We examined the effect of botulinum neurotoxin A on detrusor contractility in response to activation of L-type voltage-gated Ca(2+) channels, and efferent and afferent nerve terminals induced by 70 mM KCl, electrical field stimulation and 1 μM capsaicin, respectively.

RESULTS

Botulinum neurotoxin A inhibited electrical field stimulation induced contractions at a concentration of 10 nM or higher. The maximal inhibition at 100 nM was 70% compared to that of control strips. KCl induced contractions, which were sensitive to nifedipine, were significantly inhibited by incubation with botulinum neurotoxin A at a concentration of 3 nM or higher. Maximal inhibition at 100 nM was 30% compared to that of control strips. Capsaicin induced contractions were not inhibited by 3-hour incubation but they were significantly inhibited by overnight incubation with 100 nM botulinum neurotoxin A (30% compared to control strips). Carbachol induced contractions were not altered by incubation with botulinum neurotoxin A.

CONCLUSIONS

The order of inhibitory potency of botulinum neurotoxin A was efferent nerve terminals >L-type voltage-gated Ca(2+) channels >afferent nerve terminals. Since the inhibitory effects on L-type voltage-gated Ca(2+) channels and efferent nerve terminals were observed at similar botulinum neurotoxin A concentrations, the inhibitory effect of botulinum neurotoxin A on L-type voltage-gated Ca(2+) channels may have an important role in regulating and stabilizing bladder activity.

OnabotulinumtoxinA in the treatment of neurogenic bladder

This review examines the evidence for use of onabotulinumtoxinA in the treatment of neurogenic lower urinary tract dysfunction. Since its first use in 1988 to treat detrusor sphincter dyssynergia, use of botulinum toxin has increased in this group of patients. We discuss the mechanism of action, patient selection, dosing, efficacy, and side effect profile of this now licensed treatment option.

Insight into new potential targets for the treatment of overactive bladder and detrusor overactivity

Although overactive bladder (OAB) and detrusor overactivity (DO) are not synonyms, they share therapeutic options and partially underlying physiopathological mechanisms. The aim of this overview is to give insight into new potential targets for the treatment of OAB and DO. A narrative review was done in order to reach this goal. Ageing, pelvic floor disorders, hypersensitivity disorders, morphologic bladder changes, neurological diseases, local inflammations, infections, tumors and bladder outlet obstruction may alter the normal voluntary control of micturition, leading to OAB and DO. The main aim of pharmacotherapy is to restore normal control of micturition, inhibiting the emerging pathological involuntary reflex mechanism. Therapeutic targets can be found at the levels of the urothelium, detrusor muscles, autonomic and afferent pathways, spinal cord and brain. Increased expression and/or sensitivity of urothelial-sensory molecules that lead to afferent sensitization have been documented as a possible pathogenesis of OAB. Targeting afferent pathways and/or bladder smooth muscles by modulating activity of ligand receptors and ion channels could be effective to suppress OAB.

Modulation of purinergic neuromuscular transmission by phorbol dibutyrate is independent of protein kinase C in murine urinary bladder

Parasympathetic control of murine urinary bladder consists of contractile components mediated by both muscarinic and purinergic receptors. Using intracellular recording techniques, the purinergic component of transmission was measured as both evoked excitatory junctional potentials (EJPs) in response to electrical field stimulation and spontaneous events [spontaneous EJPs (sEJPs)]. EJPs, but not sEJPs, were abolished by the application of the Na(+) channel blocker tetrodotoxin and the Ca(2+) channel blocker Cd(2+). Both EJPs and sEJPs were abolished by the application of the P2X(1) antagonist 8,8'-[carbonylbis(imino-4,1-phenylenecarbonylimino-4,1-phenylenecarbonylimino)]bis-1,3,5-naphthalenetrisulfonic acid hexasodium salt (NF279). Application of phorbol dibutyrate (PDBu) increased electrically evoked EJP amplitudes with no effect on mean sEJP amplitudes. Similar increases in EJP amplitudes were produced by PDBu in the presence of either the nonselective protein kinase inhibitor staurosporine or the specific protein kinase C (PKC) inhibitor 2-[1-(3-dimethylaminopropyl)indol-3-yl]-3-(indol-3-yl) maleimide (GF109203X). These results suggest that PDBu increases the purinergic component of detrusor transmission through increasing neurogenic ATP release via a PKC-independent mechanism.

Treatment of refractory pain with botulinum toxins--an evidence-based review

OBJECTIVES

To provide updated information on the role of botulinum toxins in the treatment of refractory pain based on prospective, randomized, double-blind, placebo-controlled studies. DESIGN OF THE REVIEW: Class I and class II articles were searched online through PubMed (1966 to the end of January 2011) and OvidSP including ahead-of-print manuscripts.

RESULTS

Level A evidence (two or more class I studies-established efficacy): pain of cervical dystonia, chronic migraine, and chronic lateral epicondylitis. Level B evidence (one class I or two class II studies-probably effective and recommended): post-herpetic neuralgia, post-traumatic neuralgia, pain of plantar fasciitis, piriformis syndrome, and pain in total knee arthroplasty. Level C evidence (one class II study-possibly effective, may be used at discretion of clinician): allodynia of diabetic neuropathy, chronic low back pain, painful knee osteoarthritis, anterior knee pain with vastus lateralis imbalance, pelvic pain, post-operative pain in children with cerebral palsy after adductor hip release surgery, post-operative pain after mastectomy, and sphincter spasms and pain after hemorrhoidectomy. Level U evidence (efficacy not proven due to diverse class I and II results): myofascial pain syndrome and chronic daily headaches. Studies in episodic migraine and tension headaches have shown treatment failure (level A-negative).

CONCLUSION

Evidence-based data indicate that administration of botulinum toxin in several human conditions can alleviate refractory pain. The problems with some study designs and toxin dosage are critically reviewed.