Beta3-adrenoceptor agonists: possible role in the treatment of overactive bladder

The impact of pharmacotherapy on sexual function in female patients being treated for idiopathic overactive bladder: a systematic review

BACKGROUND

Overactive bladder (OAB) is a condition defined by urgency with or without incontinence which disproportionately affects female patients and has a negative impact on sexual enjoyment and avoidance behaviour. Pharmacotherapy can be considered one of the main options for treating OAB. This research set out to determine the impact of pharmacotherapy on sexual function in females with OAB.

METHODS

This research used the robust methodology of a systematic review. The clinical question was formulated using the PICO (population, intervention, control, and outcomes) format to include females being treated with pharmacotherapy (anticholinergics or beta-3 adrenergic agonists) for idiopathic OAB with the use of a validated questionnaire assessing self-reported sexual function at baseline and post-treatment. The review incorporated the MEDLINE, PubMed and EMBASE databases. The AMSTAR 2 (A Measurement Tool to Assess Systematic Reviews) appraisal tool was used to guide the review process. Two reviewers worked independently in screening abstracts, deciding on the inclusion of full-texts, data extraction and risk of bias assessment.

RESULTS

In female patients with OAB, pharmacotherapy does seem to offer at least partial improvement in self-reported sexual function outcomes after 12 weeks of therapy. Still, the value of this finding is limited by an overall poor quality of evidence. Patients with a higher degree of bother at baseline stand to benefit the most from treatment when an improvement within this health-related quality of life domain is sought.

CONCLUSION

This research should form the basis for a well-conducted randomized controlled study to accurately assess sexual function improvements in females being treated with pharmacotherapy for OAB.

Detrusor Underactivity in Men with Bladder Outlet Obstruction

Detrusor underactivity (DU) and bladder outlet obstruction (BOO) are both common troublesome causes of lower urinary tract symptoms (LUTS) and often impact on quality of life simultaneously in men. This article aims to focus on DU with BOO in male patients.

METHODS

Original articles concerning DU with BOO were identified through literature research from PubMed and EMBASE database. We selected 38 articles in our review, including those concerning pathophysiology, evaluation, treatment and predictors for a successful BOO surgery for DU.

RESULTS

DU from BOO can result from several pathophysiological mechanisms. Although urodynamic study (UDS) is considered as a precise method to diagnose DU and BOO, there are some previous studies which proposed a non-invasive method to identify DU related to BOO. The treatment goal of DU is restoring bladder contractility using medication or surgery. Releasing outlet obstruction and resistance is the main strategy to restore bladder contractility when medication to directly increase bladder contractility has had limited efficacy.

CONCLUSIONS

DU from BOO is poorly understood and is largely under-researched. The etiology and pathophysiology still need to be evaluated. Effective and safe medication to restore bladder contractility is also lacking. It remains valuable to perform further research to reveal the unknown aspects of DU.

Urothelial Calcium-Sensing Receptor Modulates Micturition Function via Mediating Detrusor Activity and Ameliorates Bladder Hyperactivity in Rats

The urothelium displays mechano- and chemosensory functions via numerous receptors and channels. The calcium-sensing receptor (CaSR) detects extracellular calcium and modulates several physiological functions. Nonetheless, information about the expression and the role of CaSR in lower urinary tract has been absent. We aimed to determine the existence of urothelial CaSR in urinary bladder and its effect on micturition function. We utilized Western blot to confirm the expression of CaSR in bladder and used immunofluorescence to verify the location of the CaSR in the bladder urothelium via colocalization with uroplakin III A. The activation of urothelial CaSR via the CaSR agonist, AC-265347 (AC), decreased urinary bladder smooth muscle (detrusor) activity, whereas its inhibition via the CaSR antagonist, NPS-2143 hydrochloride (NPS), increased detrusor activity in in vitro myography experiments. Cystometry, bladder nerve activities recording, and bladder surface microcirculation detection were conducted to evaluate the effects of the urothelial CaSR via intravesical administrations. Intravesical AC inhibited micturition reflex, bladder afferent and efferent nerve activities, and reversed cystitis-induced bladder hyperactivity. The urothelial CaSR demonstrated a chemosensory function, and modulated micturition reflex via regulating detrusor activity. This study provided further evidence of how the urothelial CaSR mediated micturition and implicated the urothelial CaSR as a potential pharmacotherapeutic target in the intervention of bladder disorders.

Role of α- and β-adrenergic signaling in phenotypic targeting: significance in benign and malignant urologic disease

The urinary tract is highly innervated by autonomic nerves which are essential in urinary tract development, the production of growth factors, and the control of homeostasis. These neural signals may become dysregulated in several genitourinary (GU) disease states, both benign and malignant. Accordingly, the autonomic nervous system is a therapeutic target for several genitourinary pathologies including cancer, voiding dysfunction, and obstructing nephrolithiasis. Adrenergic receptors (adrenoceptors) are G-Protein coupled-receptors that are distributed throughout the body. The major function of α1-adrenoceptors is signaling smooth muscle contractions through GPCR and intracellular calcium influx. Pharmacologic intervention of α-and β-adrenoceptors is routinely and successfully implemented in the treatment of benign urologic illnesses, through the use of α-adrenoceptor antagonists. Furthermore, cell-based evidence recently established the antitumor effect of α1-adrenoceptor antagonists in prostate, bladder and renal tumors by reducing neovascularity and impairing growth within the tumor microenvironment via regulation of the phenotypic epithelial-mesenchymal transition (EMT). There has been a significant focus on repurposing the routinely used, Food and Drug Administration-approved α1-adrenoceptor antagonists to inhibit GU tumor growth and angiogenesis in patients with advanced prostate, bladder, and renal cancer. In this review we discuss the current evidence on (a) the signaling events of the autonomic nervous system mediated by its cognate α- and β-adrenoceptors in regulating the phenotypic landscape (EMT) of genitourinary organs; and (b) the therapeutic significance of targeting this signaling pathway in benign and malignant urologic disease. Video abstract.

Voiding Disorders in Pediatrician's Practice

Voiding disorders result usually from functional disturbance. However, relevant organic diseases must be excluded prior to diagnosis of functional disorders. Additional tests, such as urinalysis or abdominal ultrasound are required. Further diagnostics is necessary in the presence of alarm symptoms, such as secondary nocturnal enuresis, weak or intermittent urine flow, systemic symptoms, glucosuria, proteinuria, leukocyturia, erythrocyturia, skin lesions in the lumbar region, altered sensations in the perineum. Functional micturition disorders were thoroughly described in 2006, and revised in 2015 by ICCS (International Children’s Continence Society) and are divided into storage symptoms (increased and decreased voiding frequency, incontinence, urgency, nocturia), voiding symptoms hesitancy, straining, weak stream, intermittency, dysuria), and symptoms that cannot be assigned to any of the above groups (voiding postponement, holding maneuvers, feeling of incomplete emptying, urinary retention, post micturition dribble, spraying of the urinary stream). Functional voiding disorders are frequently associated with constipation. Bladder and bowel dysfunction (BBD) is diagnosed when lower urinary tract symptoms are accompanied by problems with defecation. Monosymptomatic enuresis is the most common voiding disorder encountered by pediatricians. It is diagnosed in children older than 5 years without any other lower urinary tract symptoms. Other types of voiding disorders such as: non-monosymptomatic enuresis, overactive and underactive bladder, voiding postponement, bladder outlet obstruction, stress or giggle incontinence, urethrovaginal reflux usually require specialized diagnostics and therapy. Treatment of all types of functional voiding disorders is based on non-pharmacological recommendations (urotherapy), and such education should be implemented by primary care pediatricians.

A systematic approach to the investigation and treatment of nocturia

Level of evidence: 4.

Nanotechnology advances towards development of targeted-treatment for obesity

Obesity through its association with type 2 diabetes (T2D), cancer and cardiovascular diseases (CVDs), poses a serious health threat, as these diseases contribute to high mortality rates. Pharmacotherapy alone or in combination with either lifestyle modification or surgery, is reliable in maintaining a healthy body weight, and preventing progression to obesity-induced diseases. However, the anti-obesity drugs are limited by non-specificity and unsustainable weight loss effects. As such, novel and improved approaches for treatment of obesity are urgently needed. Nanotechnology-based therapies are investigated as an alternative strategy that can treat obesity and be able to overcome the drawbacks associated with conventional therapies. The review presents three nanotechnology-based anti-obesity strategies that target the white adipose tissues (WATs) and its vasculature for the reversal of obesity. These include inhibition of angiogenesis in the WATs, transformation of WATs to brown adipose tissues (BATs), and photothermal lipolysis of WATs. Compared to conventional therapy, the targeted-nanosystems have high tolerability, reduced side effects, and enhanced efficacy. These effects are reproducible using various nanocarriers (liposomes, polymeric and gold nanoparticles), thus providing a proof of concept that targeted nanotherapy can be a feasible strategy that can combat obesity and prevent its comorbidities.

Effects of combined treatment with fesoterodine and mirabegron in a pelvic congestion rat model: Results from in vitro and in vivo functional studies

Objectives

To examine the effect of combining a nonselective muscarinic receptor antagonist, 5‐hydroxymethyl tolterodine (an active metabolite of fesoterodine), with a β3 adrenoceptor agonist, mirabegron, in a rat model of pelvic congestion.

Methods

The rat pelvic congestion model used female Sprague‐Dawley rats with their bilateral common iliac and uterine veins ligated. Expressions of M2 and M3 receptor subtypes in the urothelium and detrusor were detected by real‐time polymerase chain reaction assays. The effects of both drugs were investigated on isolated bladder strips contracted by electrical field stimulation. in vivo single cystometry was used to assess the effects of 5‐hydroxymethyl tolterodine and mirabegron independently or in combination on bladder capacity, micturition pressure, and threshold pressure.

Results

Pelvic congestion rats showed decreased bladder capacity compared with controls, but micturition pressure and threshold pressure were unchanged. Pelvic congestion model rats also demonstrated an approximately two‐fold increase in expression of both M2 and M3 receptor subtypes in the urothelium. Additive relaxant effects of 5‐hydroxymethyl tolterodine and mirabegron were observed in vitro in the electrical field stimulation‐induced contractions of bladder strips from pelvic congestion rats. In vivo, bladder capacity was increased significantly by a combination of 5‐hydroxymethyl tolterodine and mirabegron, with the combined effect exceeding the sum of the effects of monotherapies. Micturition pressure and threshold pressure did not significantly differ between groups.

Conclusions

The combination of 5‐hydroxymethyl tolterodine with mirabegron suggests the potential of synergistic effects in a rat pelvic congestion model.

Mirabegron causes vesical and urethral relaxation in rats with spinal cord injury

The effects of solifenacin and mirabegron on vesical and urethral function were compared in rats with or without spinal cord injury (SCI). Isovolumetric cystometry and urethral pressure recording were initially performed in intact rats. Then, the bladder neck was ligated under urethane anesthesia, after which a catheter was inserted through the bladder dome for isovolumetric cystometry and another catheter was inserted into the urethra to measure urethral pressure. Solifenacin (0.03-3 mg/kg) or mirabegron (0.03-3 mg/kg) was injected intravenously, and bladder and urethral activity were recorded. To create rats with SCI, the spinal cord was transected at the lower thoracic level under isoflurane anesthesia. After 2 weeks, a catheter was inserted through the bladder dome for single cystometry and bladder activity was recorded without anesthesia following intravenous injection of solifenacin or mirabegron. Isovolumetric cystometry revealed a larger decrease in maximum bladder contraction pressure after injection of solifenacin, whereas prolongation of the interval between bladder contractions was greater with mirabegron. In SCI rats, single cystometry showed that solifenacin and mirabegron both increased bladder volume at the first non-voiding bladder contraction and decreased the maximum bladder contraction pressure. Mirabegron also increased the voided volume and decreased the percentage residual volume without altering bladder capacity. Solifenacin and mirabegron both inhibited bladder contractility, and mirabegron possibly also induced urethral relaxation. Mirabegron may be suitable for patients with overactive bladder and residual urine.

Detailed insight on β-adrenoceptors as therapeutic targets

Human G protein-coupled receptors (GPCRs), especially adrenoceptors, play a crucial role in maintaining important physiological activities including cardiovascular and pulmonary functions. Among all adrenoceptors, β-adrenoceptors are the best characterized GPCRs and possess distinctive features as drug targets. Similarly, ligands that activate/deactivate β-adrenoceptors also hold a significant position in the field of biomarker identification and drug discovery. Several studies regarding molecular characterization of the β-adrenoceptor ligands have revealed that ligands with abilities to inhibit basal or intrinsic receptor activity or prevent receptor desensitization are particularly important to efficiently manage detrimental health conditions, including chronic heart failure, asthma, chronic obstructive pulmonary disease, obesity, and diabetes. Given the importance of β-adrenoceptors as molecular targets for many pathological conditions, this review aims to provide a detailed insight on the structural and functional aspects of β-adrenoceptors, with a particular emphasis on their importance as biomarkers and therapeutic targets.

Mirabegron: a Beta-3 agonist for overactive bladder

OBJECTIVE

To review the literature regarding the efficacy and safety of mirabegron for the treatment of overactive bladder (OAB).

DATA SOURCES

A literature search was performed using MEDLINE (PubMed) prior to December 31, 2013, using the terms "mirabegron" and "randomized-controlled trial."

STUDY SELECTION/DATA EXTRACTION

All published, double-blind, randomized-controlled trials assessing mirabegron were included. Articles were reviewed and included if mirabegron was used as monotherapy and if the primary outcome analyzed drug efficacy.

DATA SYNTHESIS

The efficacy of mirabegron for the treatment of OAB has been demonstrated in the selected five randomized, placebo-controlled trials. The majority of these trials lasted 12 weeks and compared various doses of mirabegron with placebo and/or tolterodine extended-release (ER). Primary efficacy outcomes for the trials included mean number of micturitions per 24 hours and mean number of incontinence episodes per 24 hours. Included trials showed statistically significant reductions in both efficacy outcomes for various doses of mirabegron when compared with placebo.

CONCLUSION

Based on the trials reviewed, mirabegron has been efficacious in reducing mean number of micturitions and incontinence episodes per 24 hours, as well as in improving other secondary outcomes such as OAB symptoms and quality-of-life measures. Common adverse drug events seen with mirabegron include: hypertension, nasopharyngitis, urinary tract infections, headache, constipation, upper respiratory tract infection, arthralgia, diarrhea, tachycardia, abdominal pain, and fatigue. Given the efficacy and safety data currently available, mirabegron represents a reasonable alternative to antimuscarinics for patients with OAB. Future studies are needed to determine the utility of mirabegron for OAB in a variety of demographics.

Effect of co-administration of BRL-37344 and tadalafil on reduction of overactive bladder symptoms after induction of detrusor overactivity in mice1

PURPOSE

To evaluate the impact of the combination of BRL 37344 and tadalafil (TDF) on the reduction of overactive bladder (OB) symptoms.

METHODS

Thirty mice were randomized into 5 groups (G) of 6 animals each. L-NAME was used to induce DO. G1: Control; G2: L-NAME; G3: L-NAME + TDF; G4: L-NAME + BRL 37344; G5: L-NAME + TDF + BRL 37344. After 30 days of treatment, the animals were submitted to cystometry to evaluate non-voiding contractions (NVC), threshold pressure (TP), baseline pressure (BP), frequency of micturition (FM) and threshold volume (TV). Differences between the groups were analyzed with ANOVA followed by the Tukey test.

RESULTS

NVC increased in G2 (4.33±2.58) in relation to G1 (1.50±0.55). NVC decreased in G3 (2.00±1.10), G4 (1.50±1.52) and G5 (2.00±1.26) compared to G2 (p<0.05). FM decreased in G3 (0.97±0.71), G4 (0.92±0.38) and G5 (1.05±0.44) compared to G2 (p<0.05). However, the combination of TDF and BRL37344 was not more effective at increasing NVC and improving FM than either drug alone. The five groups did not differ significantly with regard to TV.

CONCLUSION

The combination of BRL 37344 and TDF produced no measurable additive effect on reduction of OB symptoms.

Respiratory dysfunction following initiation of mirabegron: A case report

Background: Mirabegron, a β3 adrenergic receptor agonist, is FDA approved for treatment of overactive bladder. Approved in 2012 in the US, there have been no reports of any effects of mirabegron on pulmonary function.

Case presentation: We report the case of a 65 year old male with a history of Parkinson's disease, OSA, and aspiration pneumonia presenting with subacute worsening dyspnea and found to have worsening restrictive ventilatory defect with a pattern consistent with neuromuscular weakness. After recalling that initiation of mirabegron correlated with onset of his worsening symptoms, the patient decided to perform a trial period off the drug. He subsequently reported prompt improvement in his respiratory symptoms, which was confirmed objectively by pulmonary function tests. In this case, mirabegron was temporally associated with subacute worsening of the patient's pulmonary restrictive physiology, with subsequent resolution after discontinuation of the medication.

Conclusions: The mechanism of this adverse effect is unknown, but we speculate that this effect may be potentially mediated by the effect of β3 adrenergic receptor agonism on skeletal muscle, in this case in a patient with pre-existing neuromuscular disease. Careful assessment of patients who develop shortness of breath while on mirabegron should include an assessment for restrictive lung disease secondary neuromuscular dysfunction. Additional study is needed of the effects of β3 agonism on skeletal muscle.

Changes in sensory proteins in the bladder urothelium of patients with chronic kidney disease and end-stage renal disease

OBJECTIVE

Patients with chronic kidney disease (CKD) or end-stage renal disease (ESRD) frequently have lower urinary tract symptoms, such as frequency, urgency, or bladder pain. This study evaluated sensory protein expression in the bladder urothelium of patients with CKD or ESRD.

METHODS

Twenty-seven patients with ESRD or CKD and urodynamically proven detrusor underactivity (DU; n = 8) or bladder oversensitivity (n = 19) were enrolled in the study. These patients, and 10 controls, underwent cystoscopic biopsies of the urothelium. Western blotting analysis was used to examine the expression of sensory proteins, namely purinergic P2X₃ , muscarinic M₂ and M₃ , and β₃ -adrenergic (AR) receptors, as well as inducible (i) and epithelial (e) nitric oxide synthase (NOS), in tissue samples. Expression was compared between CKD or ESRD patients and controls.

RESULTS

P2X₃ receptor expression was lower, whereas β₃ -AR was expression higher in the bladder urothelium of the patient group (ESRD and CKD combined) compared with controls. In addition, compared with controls, CKD patients had significantly lower P2X₃ receptor expression, whereas ESRD patients had significantly higher M₃ receptor expression. There were no significant differences in M₂ receptor, eNOS, and iNOS expression between ESRD or CKD patients and controls. Patients with DU had significantly higher M₂ and M₃ receptor expression. There were no significant differences in the expression of any protein between ESRD and CKD patients, regardless of the presence of bladder pain or anuria.

CONCLUSION

Significantly decreased P2X₃ receptor and increased β₃ -AR expression are seen in the bladder urothelium of patients with ESRD or CKD. The expression of these sensory proteins is not associated with decreased bladder capacity or anuria status in patients with ESRD or CKD.

Aegeline inspired synthesis of novel β3-AR agonist improves insulin sensitivity in vitro and in vivo models of insulin resistance

BACKGROUND AND PURPOSE

In our drug discovery program of natural product, earlier we have reported Aegeline that is N-acylated-1-amino-2- alcohol, which was isolated from the leaves of Aeglemarmelos showed anti-hyperlipidemic activity for which the QSAR studies predicted the compound to be the β3-AR agonist, but the mechanism of its action was not elucidated. In our present study, we have evaluated the β3-AR activity of novel N-acyl-1-amino-3-arylopropanol synthetic mimics of aegeline and its beneficial effect in insulin resistance. In this study, we have proposed the novel pharmacophore model using reported molecules for antihyperlipidemic activity. The reported pharmacophore features were also compared with the newly developed pharmacophore model for the observed biological activity.

EXPERIMENTAL APPROACH

Based on 3D pharmacophore modeling of known β3AR agonist, we screened 20 synthetic derivatives of Aegeline from the literature. From these, the top scoring compound 10C was used for further studies. The in-slico result was further validated in HEK293T cells co-trransfected with human β3-AR and CRE-Luciferase reporter plasmid for β3-AR activity.The most active compound was selected and β3-AR activity was further validated in white and brown adipocytes differentiated from human mesenchymal stem cells (hMSCs). Insulin resistance model developed in hMSC derived adipocytes was used to study the insulin sensitizing property. 8 week HFD fed C57BL6 mice was given 50 mg/Kg of the selected compound and metabolic phenotyping was done to evaluate its anti-diabetic effect.

RESULTS

As predicted by in-silico 3D pharmacophore modeling, the compound 10C was found to be the most active and specific β3-AR agonist with EC₅₀ value of 447 nM. The compound 10C activated β3AR pathway, induced lipolysis, fatty acid oxidation and increased oxygen consumption rate (OCR) in human adipocytes. Compound 10C induced expression of brown adipocytes specific markers and reverted chronic insulin induced insulin resistance in white adipocytes. The compound 10C also improved insulin sensitivity and glucose tolerance in 8 week HFD fed C57BL6 mice.

CONCLUSION

This study enlightens the use of in vitro insulin resistance model close to human physiology to elucidates the insulin sensitizing activity of the compound 10C and edifies the use of β3AR agonist as therapeutic interventions for insulin resistance and type 2 diabetes.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Persistence and adherence with mirabegron vs antimuscarinics in overactive bladder: Retrospective analysis of a UK General Practice prescription database

INTRODUCTION AND OBJECTIVES

Persistence with antimuscarinic (AM) drugs prescribed for overactive bladder (OAB) is poor. This study aimed to compare persistence and adherence with the beta-3-adrenoceptor agonist mirabegron (MIR) vs AMs over 12 months.

PATIENTS AND METHODS

This retrospective cohort analysis included patients aged ≥18 years who were prescribed MIR, or any AM. A 12-month look-back was used to assess inclusion eligibility. The primary end-point was persistence, defined as time to first discontinuation of index drug, during 1 year follow-up. The secondary end-point was adherence, estimated by medication possession ratio (MPR).

RESULTS

Inclusion criteria were met by 6189 patients. Those prescribed AMs were mostly treatment-naïve (range 72.9%-95.3%) vs 54.4% of MIR patients. There was greater persistence with MIR vs AM. The median number of days on therapy with MIR was 101, vs 27-56 for AMs. Patients receiving AMs were significantly more likely to discontinue than those receiving MIR (hazard ratio [HR] range 1.24-2.05, P < .01 for each AM vs MIR. In treatment-naïve patients, HRs ranged from 1.25 (solifenacin, P = .012) to 2.07 (oxybutynin IR, P < .001). In treatment-experienced patients, they ranged from 1.10 (fesoterodine, P = NS) to 2.12 (oxybutynin IR, P < .001). Adherence was greater with MIR (mean MPR 48.4%) than with AMs (range 27.6%-40.4%, P < .001). Treatment-experienced patients were significantly less likely to discontinue treatment (HR 0.87, P = .006).

DISCUSSION AND CONCLUSION

MIR was associated with a significantly longer time to discontinuation, greater persistence and better adherence than AMs. However, there was a steep decline in persistence with all drugs after 1 month. This is unlikely to be wholly explained by anticholinergic adverse events, as it was also seen with MIR. The lower proportion of MIR patients who were treatment-naive reflects current prescribing guidelines whereby MIR is prescribed after an initial generic AM trial. The study was limited by the small number of MIR patients. Study identifier: ISN 178-MA-3059.

On the Site and Mechanism of Action of β3-Adrenoceptor Agonists in the Bladder

The clinical success of mirabegron as the first β₃-adrenoceptor (AR) agonist for treatment of the overactive bladder (OAB) syndrome, has resulted in substantial interest in its site and mechanism of action. Even if the adrenergic innervation of the bladder and urethra has been well studied, the location(s) of β₃-ARs in different structures within the bladder wall and urethra, and the mode(s) of action of β₃-AR stimulation have still not been established. The recent demonstration of β₃-ARs on cholinergic nerve terminals with no immunoreactivity in urothelium or detrusor smooth muscle, is not in agreement with previous morphological studies, and functional data strongly suggest that β₃-ARs can be found these structures. However, recent studies suggest that the β₃-ARs on detrusor smooth muscle may not be the functionally most relevant. The assumption that β₃-AR activation during bladder filling inhibits acetylcholine release from parasympathetic neurons by a prejunctional mechanism and that this decreases bladder micromotions that generate afferent activity, is an attractive hypothesis. It does not exclude that other mechanisms may be contributing, and supports combined approaches to reduce afferent activity for treatment of the OAB syndrome.

Host Responses to Urinary Tract Infections and Emerging Therapeutics: Sensation and Pain within the Urinary Tract

Urinary tract infection (UTI) pathogenesis is understood increasingly at the level of the uropathogens and the cellular and molecular mediators of host inflammatory responses. However, little is known about the mediators of symptoms during UTI and what distinguishes symptomatic events from asymptomatic bacteriuria. Here, we review bladder physiology and sensory pathways in the context of an emerging literature from murine models dissecting the host and pathogen factors mediating pain responses during UTI. The bladder urothelium is considered a mediator of sensory responses and appears to play a role in UTI pain responses. Virulence factors of uropathogens induce urothelial damage that could trigger pain due to compromised bladder-barrier function. Instead, bacterial glycolipids are the major determinants of UTI pain independent of urothelial damage, and the O-antigen of lipopolysaccharide modulates pain responses. The extent of pain modulation by O-antigen can have profound effects, from abolishing pain responses to inducing chronic pain that results in central nervous system features reminiscent of neuropathic pain. Although these effects are largely dependent upon Toll-like receptors, pain is independent of inflammation. Surprisingly, some bacteria even possess analgesic properties, suggesting that bacteria exhibit a wide range of pain phenotypes in the bladder. In summary, UTI pain is a complex form of visceral pain that has significant potential to inform our understanding of bacterial pathogenesis and raises the specter of chronic pain resulting from transient infection, as well as novel approaches to treating pain.

Expressions of urothelial functional proteins in idiopathic detrusor overactivity patients refractory to antimuscarinic therapy with different urodynamic characteristics

AIMS

This study investigated the expressions of PGP9.5, P₂  X ₃ , muscarinic receptor (M3) and beta-3 adrenoreceptor (AR) in idiopathic detrusor overactivity (IDO) patients refractory to antimuscarinic treatment, and analyzed the correlation between protein expressions and clinical symptoms of IDO bladders with different urodynamic characteristics.

METHODS

Specimens of 48 IDO and 10 control patients without lower urinary tract symptoms were included. The levels of these proteins from bladder mucosa were determined by Western blotting.

RESULTS

The expression levels of β3-AR and M3 receptor were similar between IDO patients and controls. When IDO patients were divided into two subgroups, phasic DO and terminal DO, the results showed that β3-AR level in the patients with phasic DO was significantly higher than that of the controls and terminal DO (Both P < 0.05). PGP9.5 and P₂  X ₃ levels were also significantly increased in phasic DO subgroup than controls. P₂  X ₃ receptor was positively correlated with PGP9.5 and β3-AR, and negatively correlated with the first sensation of bladder filling and voided volume in phasic DO.

CONCLUSIONS

Similar expression M3 receptor and increased P₂  X ₃ levels in phasic DO, compared with the controls, indicate that dysregulation of purinergic bladder signaling may contribute to the pathogenesis of phasic DO refractory to antimuscarinics. Elevated expression of β3-AR in phasic DO but not in terminal DO patients may explain the different urodynamic characteristics of DO between the two subgroups. Our findings suggest that β3-AR agonist or P₂  X ₃ antagonist might be a good treatment choice for patients with phasic DO refractory to antimuscarinic therapy.

Caffeine as a Probable Factor for Increased Risk of OAB Development in Elderly People

OBJECTIVE

This study was conducted to compare overactive bladder (OAB) prevalence among people greater than 60 years of age who intake various doses of caffeine, as well as those who abstain from caffeine.

PATIENTS AND METHODS

A randomized observational study was carried out in Vladivostok Gerontological Hospital. A total of 1,098 retired people greater than 60 years of age (659 women and 439 men, average age 67.1 years) took part in the study. They were admitted to the in-patient department with the purpose of annual physical examination performed in accordance with the order of the Ministry of Public Health of the Russian Federation. People over age 60, who at the moment of examination were in satisfactory health condition, were included into the study. People in which OAB had been detected or who used to take antimuscarinic were excluded from the study. Assessment tools for examining the patients' lower urinary tract condition were as follows: OAB-q SF, urination diaries, and uroflowmetry.

RESULTS

In the course of the experiment conducted, we found that 1/3 of people, both men and women greater than 60 years of age, who did not previously seek medical advice due to urination troubles, had symptoms of detrusor overactivity. These symptoms were moderate and did not bother patients too much in most cases (63.4%). It was also found that most patients consumed no more than 300mg caffeine with beverages per day, with 30% and 10% of patients suffering from OAB or severe detrusor overactivity, respectively. At the same time, almost 50% of patients taking more than 300 mg of caffeine per day suffer from OAB.

CONCLUSION

48.1% of people over 60 years of age suffering from overactive detrusor symptoms consume greater than 300 mg caffeine daily, which is significantly higher than that of their peers who do not intake excessive amounts of caffeine.

Clinical use of the β3 adrenoceptor agonist mirabegron in patients with overactive bladder syndrome

Mirabegron is a β3 adrenoceptor agonist licensed for the treatment of overactive bladder symptoms, such as urinary urgency or urgency incontinence. β3 adrenoceptor activation causes detrusor muscle relaxation, but mirabegron may also act by binding other targets in the bladder, and it may also reduce activity in sensory nerves. Phase III clinical trials (SCORPIO, ARIES, and CAPRICORN) evaluated mirabegron at various doses, demonstrating reduction from baseline to endpoint in mean incontinence episodes and mean number of micturitions per 24 h (coprimary endpoints), along with health-related quality of life and a range of secondary measures. Efficacy was seen in many patients who had previously discontinued antimuscarinic therapy on the grounds of lack of efficacy or poor tolerability. Treatment emergent adverse effects were documented in a long-term study (TAURUS), mostly being of mild or moderate severity. The most frequent adverse effects were hypertension, dry mouth, constipation, and headache, with a lower incidence of dry mouth than for the antimuscarinic active comparator. Efficacy and safety are not substantially different in older patients. A urodynamic safety study in men showed no consistent effect on voiding function, but a small increase in postvoid residual. Use of mirabegron in combination with α-adrenergic blockers does not appear to increase adverse effects. Dose reduction is needed in people with severe renal failure, or moderate hepatic failure. Dose adjustment is not needed in relation to food intake. Ongoing research is evaluating the potential for combination therapy with antimuscarinics.

Influence of different doses of trospium and solifenacin on manageability of OAB symptoms with different severity in elderly men and women

Objective:

We studied the rationale for using standard and increased dosages of solifenacin and trospium against overactive bladder (OAB) symptoms of different severity among elderly patients.

Methods:

A total of 327 patients took part in the study: 199 women and 128 men older than 65 years (median age 69.1). The state of the lower urinary tracts was estimated by cystometry, ICIQ-SF and bladder diaries. Frequency of urgency urinary incontinence (UUI) was taken as a criterion of OAB symptom severity.

Result:

Administration of double-dosed trospium and solifenacin leads to decrease of frequency of UUI both in the group with severe symptoms (B1: 6.1 (0.5) →2.4 (0.9), p ⩽ 0.05), and in the group with moderate symptoms of OAB (A1: 2.8 (0.8) →0.5 (0.4), p ⩽ 0.001). Under a combination of trospium and solifenacin in doses recommended by manufacturers, UUI decreased authentically in the group with moderate symptoms (A2: 2.9 (0.5) →0.9 (0.5), p ⩽ 0.05) and unauthentically in the group with severe symptoms of detrusor dysfunction (B2: 7.0 (1.2) → 4.3 (1.5), p ⩾ 0.05). During the experiment six patients (1.8%) elected not to participate because of intolerable adverse events. Forty-seven more individuals (14.4%) felt adverse effects, among which the most frequent were: xerostomia (15 patients or 4.6%), faintness (nine patients or 3.8%), dryness of integuments (six patients or 1.8%).

Conclusion:

A standard-dose combination of solifenacin and trospium in older patients with moderate symptoms of OAB enables a good therapeutic effect in a short time without increasing risk of side effects. High therapeutic doses of antimuscarinic drugs are reasonable for older men and women with severe symptoms of OAB. Increasing the dose of simultaneous use of solifenacin and trospium yields a good therapeutic effect to correct UUI; however, it raises the hazard of appearance of adverse effects. The number of side effects in the group of elderly individuals who were taking the combination of increased and standard dosages of solifenacin and trospium does not significantly differ.

Characterization of the role of HCN channels in β3-adrenoceptor mediated rat bladder relaxation

Objective

The second messenger cAMP is involved in both β3 adrenoceptor (β3-AR) mediated detrusor relaxation and the kinetics of Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels. Here we characterized the effect HCN channel activation and possible interaction with β3-AR in bladder.

Materials and Methods

Bladder tissues from Sprague-Dawley rats and Human organ donors were obtained for studying species-specific expression of HCN channels by real-time qPCR and Western Blot. Effect of β3-agonist on rat bladder strips (0.5 × 0.5 × 7 mm in size) was studied during activation and blockade of HCN channels by Lamotrigine and ZD7288, respectively.

Results

Expression of all four genes encoding for HCN channels (HCN1-4) was detected separately in bladder mucosa and detrusor from human and rat bladders. Species based differences were evident from relatively higher expression of HCN4 isoform in human bladder and that of HCN1 in rat bladder. Western blot confirmed the findings at mRNA level. Cumulative application β3-AR agonist CL316,243 produced a concentration dependent decrease in resting tension of rat bladder strips expressed as integral of mechanical activity. Pre-incubation of HCN channel blocker ZD 7288 opposed the relaxant effect of CL316,243, whereas co-administration of lamotrigine with CL316,243 at equal molar concentrations caused an additive decrease in resting tension. Cumulative addition of ZD7288 and lamotrigine in absence of CL316,243 showed opposing effects on detrusor contractility.

Conclusions

Species-specific differences were noted in expression of HCN channels in bladder. Opposing effects ZD7288 and Lamotrigine in the action of β3-AR agonist demonstrate possible functional interaction of HCN channels and β3-AR in detrusor contractility.

A randomized, controlled trial of effectiveness and safety of management of OAB symptoms in elderly men and women with standard-dosed combination of solifenacin and mirabegron

OBJECTIVES

Comparison of effectiveness and safety of solifenacin and mirabegron, as well as their combination, for managing heavy symptoms of overactive bladder.

MATERIALS AND METHODS

All patients who participated in the examination (average age: 71.2) were split into 4 groups. Patients included in Group А (n=63) were treated with mirabegron 50mg/day/6 weeks, in Group B (n=52)-with solifenacin 10mg/day/6 weeks, in Group С (n=65)-with the same doses of both drugs simultaneously/6 weeks, and in Group D (n=59)-with placebo. Monitoring was carried out using OAB-questionnaires, bladder diaries and urodynamic examination.

RESULTS

In elderly patients with initial frequency of episodes of incontinence (EI)≥3/day standard doses of mirabegron (50mg/day) and solifenacin 10mg/day administered during 6 weeks result with the decrease in frequency of EI with high correlation (r=0,74, p≤0.05); final results in both groups are significantly different from initial value of p≤0.05. In the group, where patients were taking both drugs simultaneously, final results significantly differ from both initial values of the parameters in these groups (EI: 5.1→1.6 per day, p≤0.01; urination: 9.1→5.3 per day, p≤0.01; post-void residual 19.4→29.9, p≤0.01) and final values in Groups A and B (p≤0.05). The percentage of side effects in this group does not significantly differ from that in the groups, where patients were receiving monotherapy.

CONCLUSION

Combined treatment for severe symptoms of OAB in elderly men and women with standard doses of solifenacin and mirabegron provides satisfactory therapeutic effect within short period of time without increasing the risk of side effects, which undoubtedly improves quality of life and self-esteem of patients. At the same time, taking any of these drugs separately for the treatment of severe malfunction of lover urinary tracts in elderly people may turn out to be insufficient for effective symptom management.

Randomized controlled trial of cyclic and continuous therapy with trospium and solifenacin combination for severe overactive bladder in elderly patients with regard to patient compliance

OBJECTIVES

The aim of the study was to increase the efficiency of treatment for severe symptoms of overactive bladder (OAB) with antimuscarinic drugs in elderly men and women.

METHODS

A total of 341 patients over 65 years of age (average age 69.9; 186 women and 155 men) with severe symptoms of OAB (frequency of incontinence episodes [IEs] ≥ 3/day) underwent examination. Patients were distributed into three main groups: A (n = 58; trospium 60 mg/day + solifenacin 20): three cycles, each cycle 8 weeks, with an 8-week interval; B (n = 55; trospium 30 mg/day + solifenacin 10), regimen was the same as in group A; C (n = 62; trospium 30 mg/day + solifenacin 10) daily during 1 year.

RESULTS

The most successful treatment for the clinical and urodynamic symptoms of OAB was observed in group A, without an increase in the quantity or intensity of side effects (IEs = 4.8 (0.9) → 1.4 (0.8); p ≤ 0.01). Groups B and C also demonstrated positive effects for most of the markers for lower urinary tract state with statistical significance p ≤ 0.01. Nonparametric correlation between decrease in IEs and relative number of patients who accurately fulfilled prescriptions was in group A, r = 0.53, p ≤ 0.05; in group B, r = 0.61; p ≤ 0.05; in group C, r = 0.55, p ≤ 0.05.

CONCLUSIONS

Cyclic therapy with two different spectrum antimuscarinics appears to be effective for controlling severe OAB in elderly patients. One-year cyclic therapy with a trospium and solifenacin combination provides a high compliance level (76-84%). However, continuous therapy with standard doses of trospium and solifenacin results in low adherence and high rates of treatment withdrawals (≥ 66%) despite satisfactory clinical and urodynamic results.

Neural control of lower urinary tract and targets for pharmacological therapy

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

Understanding clinic options for overactive bladder

Overactive bladder (OAB) is a symptom complex of urinary frequency, nocturia and urgency with or without urgency incontinence that adversely impacts patient's quality of life. Conservative management begins in the outpatient clinic, often with significant improvement and patient satisfaction. In this review we will discuss the evaluation of OAB and review treatment options focusing on behavioral modification, medical therapy, and neuromodulation. These treatment options are offered in a stepwise fashion, remembering that more than one may be needed and can be used concomitantly.

Effectiveness of combined high-dosed trospium and solifenacin depending on severity of OAB symptoms in elderly men and women under cyclic therapy

MATERIAL AND METHODS

313 patients, 196 women and 117 men over 65 (average age 68.6) were included in this study. All patients underwent urodynamic examination before enrollment and after the study was completed. For clinical evaluation of LUT state ICIQ-SF questionnaires and bladder diaries were used. Patients with moderate (А, n = 155) and severe (В, n = 158) symptoms of OAB. Each group was divided into subgroups in which patients received Trospium 60 mg/day and Solifenacin 20 mg/day during two cycles - 1.5 and 1 month with one month interval (А1 and В1); subgroups in which second cycle was substituted with placebo (А2, В2), and control groups (А3, В3).

RESULTS

In groups with moderate symptoms of OAB ratio of patients demonstrated decrease of frequency of EI ≥1.5 a day remained at the level of 45-60% during all observation period. In subgroups with severe symptoms of OAB percentage of such patients was 55.3% for the subgroup which received two cycle therapy, and decreased to 26% in the subgroup which underwent 1 cycle therapy. Urodynamic indices for state of LUT correlated with clinical indicators (r =0.57-0.71 at p≤ 0.05).

CONCLUSIONS

Short single cycle of high-dosed Solifenacin and Trospium in elderly patients with moderate symptoms of OAB enables to maintain long therapeutic effect with acceptable level of side effects. This treatment algorithm applied in two cycle course is an effective and safe method for management of severe symptoms of OAB in elderly patients without increased risk of side effects.

β3-adrenergic receptor activity modulates melanoma cell proliferation and survival through nitric oxide signaling

We have recently shown in B16F10 melanoma cells that blockade of β3-adrenergic receptors (β3-ARs) reduces cell proliferation and induces apoptosis, likely through the involvement of nitric oxide (NO) signaling. Here, we tested the hypothesis that the effects of β3-AR blockade on melanoma cells are mainly mediated by a decrease in the activity of the NO pathway, possibly due to reduced expression of inducible NO synthase (iNOS). B16F10 cells were used. Nitrite production, iNOS expression, cell proliferation, and apoptosis were evaluated. β3-AR blockade with L-748,337 reduced basal nitrite production, while β3-AR stimulation with BRL37344 increased it. The effects of β3-AR blockade were prevented by NOS activation, while the effects of β3-AR activation were prevented by NOS inhibition. Treatments increasing nitrite production also increased iNOS expression, while treatments decreasing nitrite production reduced iNOS expression. Among the different NOS isoforms, experiments using L-748,337 or BRL37344 with activators or inhibitors targeting specific NOS isoforms demonstrated a prominent role of iNOS in nitrite production. β3-AR blockade decreased cell proliferation and induced apoptosis, while β3-AR activation had the opposite effects. The effects of β3-AR blockade/activation were prevented by iNOS activation/inhibition, respectively. Taken together, these results demonstrate that iNOS-produced NO is a downstream effector of β3-ARs and that the beneficial effects of β3-AR blockade on melanoma B16F10 cell proliferation and apoptosis are functionally linked to reduced iNOS expression and NO production. Although it is difficult to extrapolate these data to the clinical setting, the targeted inhibition of the β3-AR-NO axis may offer a new therapeutic perspective to treat melanomas.

Maintenance of the therapeutic effect of two high-dosage antimuscarinics in the management of overactive bladder in elderly women

PURPOSE

To improve the long-term efficiency of the pharmacologic management of overactive bladder (OAB) in elderly women.

METHODS

The study comprised 229 women (mean age, 66.3 years; range, 65-77 years) with urodynamically and clinically confirmed OAB. All patients received the most effective treatment regimen based on the data obtained in the initial part of the study (trospium 60 mg/day + solifenacin 40 mg/day, for 6 weeks), and positive results similar to those in the first phase were obtained. They were then divided into four groups, based on the maintenance therapy: group A (59 women), trospium (60 mg/day) + solifenacin (40 mg/day) for 1 month; group B (51 women), electrical stimulation of the detrusor muscle for 1 month; group C (63 women), laser puncture for 1 month; group D (56 women), placebo. Maintenance therapy was administered 2.5 months after completion of primary treatment. The patients' condition was monitored through the OAB questionnaire for 1 year and by urodynamic examination at months 6 and 7 from the start of the study.

RESULTS

In group A, the clinical and urodynamic results achieved after the initial + main treatment phase (two high-dosage antimuscarinics of different generations, trospium and solifenacin, for a total of 2.5 months) were maintained for at least 7 months. Electrical stimulation of the urinary bladder as a method of maintenance therapy proved to be less effective. In groups C and D, deterioration in results was observed at 6-8 months, which led us to conclude that laser puncture was an inefficient method of maintenance therapy in elderly women with OAB.

CONCLUSIONS

Maintenance treatment of OAB in elderly women with a combination of high-dosage antimuscarinics is an effective method for reducing the risk of recurrence of the disease.

Mirabegron, a novel, non-antimuscarinic drug for the overactive bladder: An up-to-dated review

Mirabegron opened a new era in the treatment of overactive bladder (OAB). For the first time physicians dealing with OAB have an effective alternative to the pharmacological mainstay of the therapy for this disorder, the antimuscarinic drugs. This first-in-class, potent β3-adrenoceptors agonist has recently received approval by regulatory authorities in Japan, United States and Europe, based on the favourable efficacy-tolerability profile demonstrated in multiple randomized, multinational, controlled trials, both short and long-term. There is substantial consistency through the studies in reporting the cardiovascular safety of treatment with mirabegron. The main advantage of mirabegron is the placebo-like incidence of classic adverse effects caused by antimuscarinics, dry mouth and constipation, that is expected to improve long-term adherence of patients to treatment. Mirabegron can be used in patients with contraindications to antimuscarinics and in those who discontinued previous antimuscarinic therapy. Herein, we reviewed the published literature on mirabegron, focusing on the rationale of β3-agonism for OAB treatment and on the preclinical and clinical evidence of efficacy and safety available on this new pharmacological principle.

Impact of mirabegron extended-release on the treatment of overactive bladder with urge urinary incontinence, urgency, and frequency

Overactive bladder is a highly prevalent disorder with a significant impact on quality of life. Antimuscarinic agents are commonly used, but persistence is limited due to unsatisfactory efficacy and/or tolerability. Mirabegron is the first beta-3 adrenoceptor agonist approved for the treatment of overactive bladder syndrome. This paper reviews the pharmacology, mechanism of action, efficacy, and safety of mirabegron. A PubMed search of all English articles pertaining to mirabegron was performed. An alternative to antimuscarinics, mirabegron has a unique mechanism, improves overactive bladder symptoms and quality of life, and has limited adverse effects and few contraindications.

The efficacy and safety of mirabegron in treating OAB: a systematic review and meta-analysis of phase III trials

PURPOSE

Mirabegron, a potent and selective β3-adrenoceptor agonist, has been developed for the treatment of overactive bladder (OAB). We carried out a systematic review and meta-analysis to assess the efficacy and safety of the drug for treating OAB.

METHODS

A literature review was performed to identify all published randomized double-blind, placebo-controlled phase III trials of mirabegron for the treatment of OAB. The search included the following databases: MEDLINE, EMBASE and the Cochrane Controlled Trials Register. The reference lists of the retrieved studies were also investigated. A systematic review and meta-analysis of phase III trials were conducted.

RESULTS

Four publications involving a total of 5,761 patients were used in the analysis, including four phase III RCTs that compared mirabegron with placebo. We found that mirabegron was effective in treating OAB in our meta-analysis. Co-primary efficacy end points: the mean number of incontinence episodes per 24 h (the standardized mean difference (SMD) = -0.44, 95 % confidence interval (CI) -0.59 to -0.29, p < 0.00001); the mean number of micturitions per 24 h (SMD = -0.62, 95 % CI -0.80 to -0.45, p < 0.00001) and key secondary efficacy end points: mean volume voided per micturition; mean number of urgency episodes per 24 h indicated that mirabegron was more effective than the placebo. Safety assessments included common treatment-emergent adverse events (TEAEs) [OR 1.10, 95 % CI 0.93-1.31, p = 0.25), hypertension, cardiac arrhythmia TEAEs, urinary retention and discontinuations due to adverse event indicated that mirabegron was well tolerated.

CONCLUSIONS

This meta-analysis indicates that mirabegron to be an effective and safe treatment for OAB symptoms with a low occurrence of side effects. It offers promise as an effective oral agent for the treatment of OAB with a distinct efficacy/tolerability balance.

Urothelial signaling

The urothelium, which lines the inner surface of the renal pelvis, the ureters, and the urinary bladder, not only forms a high-resistance barrier to ion, solute and water flux, and pathogens, but also functions as an integral part of a sensory web which receives, amplifies, and transmits information about its external milieu. Urothelial cells have the ability to sense changes in their extracellular environment, and respond to chemical, mechanical and thermal stimuli by releasing various factors such as ATP, nitric oxide, and acetylcholine. They express a variety of receptors and ion channels, including P2X3 purinergic receptors, nicotinic and muscarinic receptors, and TRP channels, which all have been implicated in urothelial-neuronal interactions, and involved in signals that via components in the underlying lamina propria, such as interstitial cells, can be amplified and conveyed to nerves, detrusor muscle cells, and ultimately the central nervous system. The specialized anatomy of the urothelium and underlying structures, and the possible communication mechanisms from urothelial cells to various cell types within the bladder wall are described. Changes in the urothelium/lamina propria ("mucosa") produced by different bladder disorders are discussed, as well as the mucosa as a target for therapeutic interventions.

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

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

In vitro and in vivo pharmacological profile of the selective β3-adrenoceptor agonist mirabegron in rats

To investigate the pharmacological properties of mirabegron in in vitro and in vivo, the effects on cAMP accumulation in Chinese hamster ovary (CHO) cells expressing rat β-adrenoceptors, the relaxant activity in isolated rat bladder smooth muscle, and the voiding effects in cerebral infarcted rats were evaluated. Mirabegron increased cAMP accumulation with EC(50) value and intrinsic activity of 19 nmol/L and 1.0, respectively, in CHO cells expressing rat β(3)-adrenoceptors. The EC(50) values and the intrinsic activities of mirabegron were 610 nmol/L and 0.6 for rat β(1)-adrenoceptors and were sumless and 0.1 for β(2)-adrenoceptors, respectively. Mirabegron showed concentration-dependent relaxant and full agonistic effects in rat bladder strips under passive tension with EC(50) value of 290 nmol/L. The concentration-response curve of mirabegron was affected neither by the β(1)-adrenoceptor selective antagonist CGP-20712A nor by the β(2)-adrenoceptor selective antagonist ICI-118,551. In in vivo studies with cerebral infarcted rats, a significant decrease in the volume voided per micturition compared with sham-operated rats was observed. Mirabegron dose-dependently increased the volume voided per micturition. In conclusion, we have extended the selectivity profile of mirabegron to rats and demonstrated that it is effective via stimulation of β(3)-adrenoceptors in a rat cerebral infarction model of detrusor overactivity.

The novel β3-adrenoceptor agonist mirabegron reduces carbachol-induced contractile activity in detrusor tissue from patients with bladder outflow obstruction with or without detrusor overactivity

β(3)-Adrenoceptors are major players in detrusor relaxation and have been suggested as a new putative target for the treatment of overactive bladder syndrome. We determined the effects of mirabegron (YM178), a novel β(3)-adrenoceptor agonist, on carbachol-induced tone in isolated human detrusor preparations from patients with bladder outflow obstruction (BOO) with and without detrusor overactivity (DO), and from patients with normal bladder function. We compared the effects to those of isoprenaline, a non-selective β-adrenoceptor agonist. Detrusor specimens were obtained from patients with benign prostatic hyperplasia undergoing cystoscopy and from patients undergoing radical prostatectomy/cystectomy (in total 33 donors). Detrusor contractility was evaluated by organ bath studies and strips were incubated with carbachol (1μM) to induce and enhance tension. Both mirabegron and isoprenaline reduced carbachol-induced tone in tissues from all groups. Isoprenaline decreased tension with higher potency than mirabegron in normal, BOO and BOO+DO detrusor strips with pIC(50) values of 7.49 ± 0.16 vs. 6.23 ± 0.26 (P=0.0002), 6.89 ± 0.34 vs. 6.04 ± 0.31 (P=0.01), and 6.57 ± 0.20 vs. 5.41 ± 0.08 (P<0.0001, n=4), respectively. The maximal relaxant effect of isoprenaline and mirabegron in the normal, BOO and BOO+DO detrusor was 37.7 ± 14.4% and 36.1 ± 23.3%, 14.4 ± 12.2% vs. 33.4 ± 21.0% and 18.3 ± 10.0% vs. 28.3 ± 12.2% (n=4, P>0.05), respectively. Mirabegron and isoprenaline reduced carbachol-induced tone in both normal bladders and obstructed bladder with and without DO. Isoprenaline had higher potency than mirabegron, but the efficacy of mirabegron effect was the same as that of isoprenaline.

Mirabegron: a review of recent data and its prospects in the management of overactive bladder

Mirabegron is a novel, once-daily, orally active, first-in-class, potent β(3)-adrenoceptor agonist recently approved by Food and Drug Administration for overactive bladder therapy. Phase II studies and four large-scale phase III multinational randomized, controlled trials have supported the efficacy and tolerability of mirabegron in the clinical trial setting of patients with overactive bladder for up to 12 weeks of therapy and in the long term (12 months). The reported incidence and severity of treatment-emergent and serious adverse effects were similar to antimuscarinics, but with a more than threefold lower incidence of dry mouth compared with tolterodine. However, the effects on the cardiovascular system, pharmacokinetic interactions with other drugs, and increased incidence of new malignant events will require careful evaluation in the near future.

Mirabegron - a selective β3-adrenoreceptor agonist for the treatment of overactive bladder

Overactive bladder is a common condition that significantly impacts overall quality of life. Antimuscarinics are the current main pharmacological option for treatment; however, many patients fail to adhere to therapy due to troublesome side effects. Mirabegron is a new beta-3 adrenoreceptor agonist which causes detrusor smooth muscle relaxation and has been proposed to be effective for treating overactive bladder symptoms. Mirabegron has been shown to be superior to placebo for reducing the mean number of incontinence episodes per 24 hours and the mean number of micturitions per 24 hours. Side effects such as dry mouth were observed at similar or lower rates than those seen for placebo and antimuscarinics. Higher doses of mirabegron were associated with minor increases in pulse rate and mean blood pressure. Mirabegron offers a new alternative for treating overactive bladder in patients for which antimuscarinics are either not tolerated or not appropriate.