ATP during early bladder stretch is important for urgency in detrusor overactivity patients

Extracellular nucleotides in smooth muscle contraction

Extracellular nucleotides and nucleosides are crucial signalling molecules, eliciting diverse biological responses in almost all organs and tissues. These molecules exert their effects by activating specific nucleotide receptors, which are finely regulated by ectonucleotidases that break down their ligands. In this comprehensive review, we aim to elucidate the relevance of extracellular nucleotides as signalling molecules in the context of smooth muscle contraction, considering the modulatory influence of ectonucleotidases on this intricate process. Specifically, we provide a detailed examination of the involvement of extracellular nucleotides in the contraction of non-vascular smooth muscles, including those found in the urinary bladder, the airways, the reproductive system, and the gastrointestinal tract. Furthermore, we present a broader overview of the role of extracellular nucleotides in vascular smooth muscle contraction.

Urinary ATP may be a biomarker of interstitial cystitis/bladder pain syndrome and its severity

Urinary tract cells respond to bladder distension by releasing adenosine triphosphate (ATP). Patients with interstitial cystitis/bladder pain syndrome (IC/BPS) exhibit elevated urinary ATP levels compared to asymptomatic controls. This study aimed to evaluate the potential of urinary ATP as a non-invasive biomarker for IC/BPS and its correlation with symptom severity. We included 56 patients diagnosed with IC/BPS and 50 asymptomatic controls. Urine samples were collected from both groups. Urinary ATP levels were quantified using the luciferin-luciferase bioluminescence method. The severity of IC/BPS symptoms was assessed using the visual analogue score (VAS), Interstitial Cystitis Symptom Index (ICSI), and Interstitial Cystitis Problem Index (ICPI) from the O'Leary-Sant score. We specifically examined the correlation between symptom scores and urinary ATP levels in IC/BPS patients. Urinary ATP levels were significantly higher in IC/BPS patients compared to the control group (P < 0.0001). There was a significant positive correlation between urinary ATP concentrations and VAS, ICPI, and ICSI scores among IC/BPS patients (P < 0.0001). The threshold value for ATP concentration was set at 56.6 nM, with an area under the receiver operating characteristic (ROC) curve of 0.811 (95% CI 0.730 - 0.892). Our findings indicate that IC/BPS patients excrete elevated amounts of ATP in their urine. This suggests that urinary ATP might serve as a non-invasive biomarker for IC/BPS, with a predictive potential in terms of symptom severity.

Mechanotransduction in the urothelium: ATP signalling and mechanoreceptors

The urothelium, which covers the inner surface of the bladder, is continuously exposed to a complex physical environment where it is stimulated by, and responds to, a wide range of mechanical cues. Mechanically activated ion channels endow the urothelium with functioning in the conversion of mechanical stimuli into biochemical events that influence the surface of the urothelium itself as well as suburothelial tissues, including afferent nerve fibres, interstitial cells of Cajal and detrusor smooth muscle cells, to ensure normal urinary function during the cycle of filling and voiding. However, under prolonged and abnormal loading conditions, the urothelial sensory system can become maladaptive, leading to the development of bladder dysfunction. In this review, we summarize developments in the understanding of urothelial mechanotransduction from two perspectives: first, with regard to the functions of urothelial mechanotransduction, particularly stretch-mediated ATP signalling and the regulation of urothelial surface area; and secondly, with regard to the mechanoreceptors present in the urothelium, primarily transient receptor potential channels and mechanosensitive Piezo channels, and the potential pathophysiological role of these channels in the bladder. A more thorough understanding of urothelial mechanotransduction function may inspire the development of new therapeutic strategies for lower urinary tract diseases.

Sensory Neurons, PIEZO Channels and PAC1 Receptors Regulate the Mechanosensitive Release of Soluble Ectonucleotidases in the Murine Urinary Bladder Lamina Propria

The urinary bladder requires adequate concentrations of extracellular adenosine 5'-triphosphate (ATP) and other purines at receptor sites to function properly. Sequential dephosphorylation of ATP to ADP, AMP and adenosine (ADO) by membrane-bound and soluble ectonucleotidases (s-ENTDs) is essential for achieving suitable extracellular levels of purine mediators. S-ENTDs, in particular, are released in the bladder suburothelium/lamina propria (LP) in a mechanosensitive manner. Using 1,N⁶-etheno-ATP (eATP) as substrate and sensitive HPLC-FLD methodology, we evaluated the degradation of eATP to eADP, eAMP and eADO in solutions that were in contact with the LP of ex vivo mouse detrusor-free bladders during filling prior to substrate addition. The inhibition of neural activity with tetrodotoxin and ω-conotoxin GVIA, of PIEZO channels with GsMTx4 and D-GsMTx4 and of the pituitary adenylate cyclase-activating polypeptide type I receptor (PAC1) with PACAP6-38 all increased the distention-induced but not spontaneous release of s-ENTDs in LP. It is conceivable, therefore, that the activation of these mechanisms in response to distention restricts the further release of s-ENTDs and prevents excessive hydrolysis of ATP. Together, these data suggest that afferent neurons, PIEZO channels, PAC1 receptors and s-ENTDs form a system that operates a highly regulated homeostatic mechanism to maintain proper extracellular purine concentrations in the LP and ensure normal bladder excitability during bladder filling.

Pathophysiological Mechanisms Involved in Overactive Bladder/Detrusor Overactivity

Purpose of Review

To examine the latest published findings on the pathophysiological mechanisms involved in the development of overactive bladder (OAB) and detrusor overactivity (DO), and to identify common pathways linked to the risk factors associated with these conditions.

Recent Findings

Evidence is accumulating, both clinical and experimental, that many of the factors linked to the development of OAB/DO, including ageing, bladder outlet obstruction, psychological stress, and obesity are associated with reduced bladder blood flow. This induces local tissue inflammation with cytokine release and enhanced oxidative stress, ultimately resulting in altered detrusor sensitivity, detrusor hypertrophy and fibrosis, together with afferent hypersensitivity. These mechanisms would explain the symptoms of urgency and frequency observed in OAB patients. Although not a characteristic of OAB, undetected low level bacterial infections of the bladder have been proposed to explain the OAB symptoms in patients resistant to standard treatments. In this condition, inflammatory responses without reductions in perfusion activate the inflammatory pathways.

Summary

Evidence is mounting that poor bladder perfusion and local inflammatory responses are central mechanisms involved in the development of OAB/DO. As our understanding of these pathophysiological mechanisms advances, new avenues for drug development will be identified and ultimately treatment may become more individualized depending on the particular pathway involved and the drugs available.

Urinary ATP Levels Are Controlled by Nucleotidases Released from the Urothelium in a Regulated Manner

Adenosine 5′-triphosphate (ATP) is released in the bladder lumen during filling. Urothelial ATP is presumed to regulate bladder excitability. Urinary ATP is suggested as a urinary biomarker of bladder dysfunctions since ATP is increased in the urine of patients with overactive bladder, interstitial cystitis or bladder pain syndrome. Altered urinary ATP might also be associated with voiding dysfunctions linked to disease states associated with metabolic syndrome. Extracellular ATP levels are determined by ATP release and ATP hydrolysis by membrane-bound and soluble nucleotidases (s-NTDs). It is currently unknown whether s-NTDs regulate urinary ATP. Using etheno-ATP substrate and HPLC-FLD detection techniques, we found that s-NTDs are released in the lumen of ex vivo mouse detrusor-free bladders. Capillary immunoelectrophoresis by ProteinSimple Wes determined that intraluminal solutions (ILS) collected at the end of filling contain ENTPD3 > ENPP1 > ENPP3 ≥ ENTPD2 = NT5E = ALPL/TNAP. Activation of adenylyl cyclase with forskolin increased luminal s-NTDs release whereas the AC inhibitor SQ22536 had no effect. In contrast, forskolin reduced and SQ22536 increased s-NTDs release in the lamina propria. Adenosine enhanced s-NTDs release and accelerated ATP hydrolysis in ILS and lamina propria. Therefore, there is a regulated release of s-NTDs in the bladder lumen during filling. Aberrant release or functions of urothelial s-NTDs might cause elevated urinary ATP in conditions with abnormal bladder excitability.

P2 purinergic receptor dysregulation in urologic disease

P2 purinergic receptors are involved in the normal function of the kidney, bladder, and prostate via signaling that occurs in response to extracellular nucleotides. Dysregulation of these receptors is common in pathological states and often associated with disease initiation, progression, or aggressiveness. Indeed, P2 purinergic receptor expression is altered across multiple urologic disorders including chronic kidney disease, polycystic kidney disease, interstitial cystitis, urinary incontinence, overactive bladder syndrome, prostatitis, and benign prostatic hyperplasia. P2 purinergic receptors are likewise indirectly associated with these disorders via receptor-mediated inflammation and pain, a common characteristic across most urologic disorders. Furthermore, select P2 purinergic receptors are overexpressed in urologic cancer including renal cell carcinoma, urothelial carcinoma, and prostate adenocarcinoma, and pre-clinical studies depict P2 purinergic receptors as potential therapeutic targets. Herein, we highlight the compelling evidence for the exploration of P2 purinergic receptors as biomarkers and therapeutic targets in urologic cancers and other urologic disease. Likewise, there is currently optimism for P2 purinergic receptor-targeted therapeutics for the treatment of inflammation and pain associated with urologic diseases. Further exploration of the common pathways linking P2 purinergic receptor dysregulation to urologic disease might ultimately help in gaining new mechanistic insight into disease processes and therapeutic targeting.

The use of urinary biomarkers in the diagnosis of overactive bladder in female patients. A systematic review and meta-analysis

INTRODUCTION AND HYPOTHESIS

Nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and other proteins are related to overactive bladder (OAB) syndrome, as their urinary concentrations are significantly different from those of the general non-OAB population. This review aims to systematically assess whether NGF, BDNF, and other urinary by-products can be used as potential biomarkers to manage women with OAB.

METHODS

This was a systematic review and metanalysis that was conducted according to PRISMA guidelines. Studies were identified by electronic search of Medline, Scopus, ScienceDirect, Embase, and Cochrane Register until October 2020. The included studies investigated the correlation of OAB with NGF, BDNF, and other potential biomarkers in symptomatic women and their controls.

RESULTS

Twelve studies (581 female OAB patients and 394 female controls) were included. Urinary NGF, NGF/Cr, BDNF/Cr, ATP/Cr, and PGE2/Cr ratios were identified as potential biomarkers in female OAB patients. Results of the meta-analysis indicated that uNGF [standard mean difference (SMD) 1.45, 95% CI 0.53-2.36], NGF/Cr ratio (SMD 1.23, 95% CI 0.67-1.78), BDNF/Cr ratio (SMD 0.78, 95% CI 0.006-1.50), and BDNF/Cr ratio (RR 0.78, 95% CI 0.006-1.50) were increased in female OAB patients compared to healthy controls, whereas no difference was found for the PGE2/Cr and ATP/Cr ratios. Current data are inadequate to assess any other potential biomarkers, such as urinary MDA, ATP, and cytokines, in the management of OAB in female patients.

CONCLUSIONS

uNGF, NGF/Cr, and BDNF/Cr ratio could be used in the assessment of female OAB patients. Further studies are needed to specify OAB urinary titer levels in OAB subgroups and healthy women and their potential as diagnostic and management tools in OAB women.

Purinergic signalling in the urinary bladder - When function becomes dysfunction

Knowledge of the participation of ATP and related purines in urinary tract physiology has been established over the last five decades through the work of many independent groups, inspired by, and building on the pioneering studies of Professor Geoffrey Burnstock and his coworkers. As part of a series of reviews in this tribute edition, the present article summarises our current understanding of purines and purinergic signalling in modulating and regulating urinary tract function. Purinergic mechanisms underlying the origin of bladder pain; sensations of bladder filling and urinary tract motility; and regulation of detrusor smooth muscle contraction are described, encompassing the relevant history of discovery and consolidation of knowledge as methodologies and pharmacological tools have developed. We consider normal physiology, including development and ageing and then move to pathophysiology, discussing the causal and consequential contribution of purinergic signalling mechanism and their constituent components (receptors, signal transduction, effector molecules) to bladder dysfunction.

Chronic psychological stress and lower urinary tract symptoms

It is well established that lower urinary tract symptoms (LUTS), particularly urinary urgency and incontinence, cause stress and anxiety for patients. However, there is mounting evidence that the relationship between these two factors is bidirectional and that chronic psychological stress itself can result in the development of symptoms such as urinary frequency, urgency, incontinence, and pelvic pain. This review considers the evidence that such a relationship exists and reviews the literature from clinical and animal studies to identify some of the mechanisms that might be involved. Inflammatory responses induced by chronic stress appear to offer the strongest link to bladder dysfunction. There is overwhelming evidence, both in patients and animal models, for a release of pro-inflammatory cytokines and chemokines during periods of chronic stress. Furthermore, cytokines have been shown to cause bladder dysfunction and pain via actions in the central nervous system and locally in the bladder. In the brain and spinal cord, pro-inflammatory cytokines influence the regulation of micturition pathways by corticotropin-releasing factor (CRF) and its receptors, while peripherally cytokines affect bladder function, directly causing detrusor hypertrophy and afferent nerve hypersensitivity. There is little information on which treatments may have most benefit for stressed/anxious patients with LUTS, but animal studies suggest traditional drugs for overactive bladder (solifenacin, mirabegron) are more effective on LUTS than anxiolytic drugs (fluoxetine, imipramine). The preliminary preclinical data for CRF receptor antagonists is not consistent. A clearer understanding of the mechanisms involved in stress-induced LUTS should provide a basis for improved treatment of this condition.

Bladder urothelium converts bacterial lipopolysaccharide information into neural signaling via an ATP-mediated pathway to enhance the micturition reflex for rapid defense

When bacteria enter the bladder lumen, a first-stage active defensive mechanism flushes them out. Although urinary frequency induced by bacterial cystitis is a well-known defensive response against bacteria, the underlying mechanism remains unclear. In this study, using a mouse model of acute bacterial cystitis, we demonstrate that the bladder urothelium senses luminal extracellular bacterial lipopolysaccharide (LPS) through Toll-like receptor 4 and releases the transmitter ATP. Moreover, analysis of purinergic P2X₂ and P2X₃ receptor-deficient mice indicated that ATP signaling plays a pivotal role in the LPS-induced activation of L6–S1 spinal neurons through the bladder afferent pathway, resulting in rapid onset of the enhanced micturition reflex. Thus, we revealed a novel defensive mechanism against bacterial infection via an epithelial-neural interaction that induces urinary frequency prior to bacterial clearance by neutrophils of the innate immune system. Our results indicate an important defense role for the bladder urothelium as a chemical-neural transducer, converting bacterial LPS information into neural signaling via an ATP-mediated pathway, with bladder urothelial cells acting as sensory receptor cells.

The Urothelium: Life in a Liquid Environment

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

Stretch- and carbachol-induced ATP release from bladder wall preparations of young and aged mice

AIMS

Bladder wall stretch increases tissue tension and releases adenosine 5'-triphosphate (ATP) as part of a transduction process to sense bladder filling. Aging is associated with bladder fibrosis to produce a stiffer bladder wall: this may augment ATP release and contribute to age-dependent urgency. Muscarinic agonists also release ATP and present a potential target for antimuscarinic agents, but its age-dependency is unknown. This study aimed, in young and old mice, to: (a) quantify the relationship between bladder wall stiffness and stretch-dependent ATP release and; (b) characterize muscarinic agonist-dependent release.

METHODS

ATP release from young (9-12 weeks) and aged (24 months) mouse bladder wall was measured in vitro, with a luciferin-luciferase assay, after stretch or carbachol exposure. Bladder wall stiffness, measured simultaneously during stretch, was compared to histological proportions of connective tissue and detrusor muscle.

RESULTS

With young mice, stretch-activated ATP release required an intact mucosa and was positively associated with wall stiffness. ATP release by carbachol was about four-fold greater compared to stretch. With aged mice: ATP release varied a hundred-fold and no association with stiffness; carbachol release diminished; connective tissue and mucosa thickness increased.

CONCLUSIONS

With young mice, stretch, or muscarinic agonists potently induce bladder wall ATP release. Stretch-dependent release is proportional to bladder wall stiffness, independent of the extent of stretch. With aged mice dependence of stretch-activated ATP release with stiffness was lost. The huge variability of release suggests that aged mice do not form a homogenous cohort and may underlie the heterogeneity in bladder filling sensations.

Urinary ATP may be a biomarker for bladder outlet obstruction and its severity in patients with benign prostatic hyperplasia

Background

Urothelial cells release ATP into the urine in response to bladder stretch. Urinary ATP concentration in benign prostatic hyperplasia (BPH) patients was higher compared with asymptomatic controls. In this study, we aimed to explore the possibility that the urinary ATP level could be a non-invasive biomarker for bladder outlet obstruction (BOO) and its severity in BPH patients.

Methods

We included 117 BPH patients who underwent urodynamic studies and 109 asymptomatic controls. Urine samples at normal desire (from patients and controls), instilled fluids at maximum cystometric capacity (capacity fluid), and voided fluids during a pressure-flow study (only from patients) were collected. The ATP concentration in collected samples was measured using a luciferin-luciferase bioluminescence assay and normalized to urine creatinine (ATP/Cr). The degree of BOO was quantified using the BOO index (BOOI). Correlation between urodynamic parameters and urinary ATP concentration was analyzed in BPH patients.

Results

Urinary ATP concentration of BPH patients was significantly higher compared with controls (P<0.001). For BPH patients, a significant positive correlation was found between urinary ATP concentration and BOOI (P<0.0001). Although BPH patients with detrusor overactivity or a history of acute urinary retention had increased urinary ATP, a significant positive correlation between ATP and BOOI was also observed in these patients. When BOOI >40 was set as a cutoff point to differentiate BOO from non-BOO patients, the area under the receiver operating characteristic (ROC) curve was 0.77 (P<0.001).

Conclusions

BPH patients with BOO released higher amounts of ATP into the urine. Urinary ATP can be used as a non-invasive biomarker of BOO, and its level may also have a predictive value for the degree of obstruction.

Design and Synthesis of Ag Nanocluster Molecular Beacon for Adenosine Triphosphate Detection

This study presents a fluorescence method for detecting adenosine triphosphate (ATP) based on a label-free Ag nanocluster molecular beacon (MB) with high sensitivity. The sensor contains a hairpin-shaped MB, two short single-stranded DNA strands, and T4 DNA ligase. The MB consists of three parts, which are the template DNA sequence for synthesizing Ag nanoclusters at the 5' end, the middle DNA with a hairpin-shaped structure, and the guanine base-rich DNA sequence at the 3' end. The sensor exhibits high fluorescence intensity in the absence of ATP. However, when the probe is used for ATP detection, the two short DNA sequences in the sensor would form a long sequence by enzymatic ligation reaction; this long sequence opens the hairpin-shaped structure of the MB and decreases the fluorescence of the system. Under optimal analytical conditions, a clear linear relationship is observed between ATP concentration and fluorescence intensity in the range of 0.1-10 μM. The interference presented by other small molecules during ATP detection is evaluated, and results confirm the good selectivity of the proposed sensor. Compared with traditional methods, the sensor is label free, easy to operate, inexpensive, and highly sensitive.

Urinary Biomarkers in Overactive Bladder: Revisiting the Evidence in 2019

CONTEXT

In overactive bladder (OAB), after an initial outbreak of research, it is more consensual that biomarkers may be better used to phenotype patients. Herein, we revisit this topic, including some of the most promising biomarkers.

OBJECTIVE

To provide a comprehensive analysis of the actual role of biomarkers in OAB.

EVIDENCE ACQUISITION

A PubMed-based literature search was conducted, including the most relevant articles published in the last 15 yr, on nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), adenosine triphosphate (ATP), genomics, and microbiota as OAB biomarkers. Articles with no full text available or not written in English were excluded. Additional reviews were included.

EVIDENCE SYNTHESIS

Urinary NGF, BDNF, and ATP are increased in many OAB patients. These biomarkers can help identify OAB phenotypes and select the ideal candidates for new therapies directed to neurotrophic and purinergic pathways. Circulating urinary miRNA may be useful for establishing the ideal moment for bladder outlet obstruction relief and will eventually lead to the development of therapeutic agents that inhibit or reverse fibrotic pathways in the bladder. Urinary microbiota seems to be related to OAB symptoms, in particular urgency urinary incontinence, and may have strong implications in the prevention, diagnosis, and treatment of OAB.

CONCLUSIONS

In the future, physicians may consider the use of biomarkers to identify distinct OAB phenotypes, with distinct causal mechanisms, selecting patients for specific target therapies with expected better outcomes.

PATIENT SUMMARY

Overactive bladder biomarkers can be useful for phenotype patients and for selecting more effective target therapies.

Influence of sildenafil on the purinergic components of nerve-mediated and urothelial ATP release from the bladder of normal and spinal cord injured mice

Background and purpose

PDE inhibitors such as sildenafil alleviate lower urinary tract symptoms; however, a complete understanding of their action on the bladder remains unclear. We are investigating the effects of sildenafil, on post and preganglionic nerve‐mediated contractions of the mouse bladder, and neuronal and urothelial ATP release.

Experimental approach

Bladders were used from young (12 weeks), aged (24 months), and spinal cord transected (SCT), mice, for in vitro contractility experiments. An arterially perfused in situ whole mouse model was used to record bladder pressure. Nerve‐mediated contractions were generated by electrical field stimulation (EFS) of postganglionic nerve terminals or the pelvic nerve. ATP release during EFS in intact detrusor strips, and during stretch of isolated mucosa strips, was measured using a luciferin‐luciferase assay.

Key results

Sildenafil (20 μM) inhibited nerve‐mediated contractions in young mice, with an increase in f_1/2 values in force–frequency relationships, demonstrating a greater effect at low frequencies. Sildenafil reduced the atropine‐resistant, purinergic component of nerve‐mediated contractions, and suppressed neuronal ATP release upon EFS in vitro. Sildenafil reduced the preganglionic pelvic nerve stimulated bladder pressure recordings in situ; comparable to in vitro experiments. Sildenafil reduced stretch‐induced urothelial ATP release. Sildenafil also relaxed nerve‐mediated contractions in aged and SCT mice.

Conclusion and implications

Sildenafil has a greater effect on the low‐frequency, purinergic‐mediated contractions and suppresses neuronal ATP release. In addition, sildenafil reduces stretch‐induced urothelial ATP release. These results demonstrate a novel action of sildenafil to selectively inhibit ATP release from nerve terminals innervating detrusor smooth muscle and the urothelium.

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

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

Potential Biomarkers for Diagnosis of Overactive Bladder Patients: Urinary Nerve Growth Factor, Prostaglandin E2, and Adenosine Triphosphate

Purpose

This study aimed to investigate potential biomarkers for the diagnosis of overactive bladder (OAB).

Methods

A total of 219 subjects were enrolled and divided into 2 groups: OAB subjects (n=189) and controls without OAB symptoms (n=30). Three-day voiding diaries and questionnaires were collected, and urinary levels of nerve growth factor (NGF), prostaglandin E2, and adenosine triphosphate were measured and normalized to urine creatinine (Cr). Baseline characteristics and urinary levels of markers were analyzed. A receiver-operator characteristic (ROC) curve was used to analyze the diagnostic performance of urinary markers. Urinary levels of markers according to subgroup and pathogenesis of OAB were evaluated. Correlation analyses were used to analyze the relationship between urinary levels of markers and voiding diary parameters and questionnaires.

Results

There was no difference between the 2 groups with regards to age, sex ratio, or urine Cr (P>0.05). The urinary levels of NGF/Cr were higher in OAB subjects than in controls (P<0.001). Urinary NGF/Cr was a sensitive biomarker for discriminating OAB patients (area under the curve=0.741; 95% confidence interval, 0.62–0.79; P=0.001) in the ROC curve. The urinary levels of NGF/Cr were significantly higher in OAB subjects than in controls regardless of subgroup or pathogenesis. Correlation analysis demonstrated urinary urgency was significantly related to urinary NGF/Cr level (correlation coefficient, 0.156). Limitations include a relatively wide variation of urinary markers.

Conclusions

Urinary NGF is a potential biomarker that could serve as a basis for adjunct diagnosis of OAB.

Changes in Adenosine Triphosphate and Nitric Oxide in the Urothelium of Patients with Benign Prostatic Hyperplasia and Detrusor Underactivity

PURPOSE

We investigated changes in the levels of adenosine triphosphate and nitric oxide in the urothelium of men with detrusor underactivity and benign prostatic hyperplasia.

MATERIALS AND METHODS

We prospectively enrolled in study 30 men who planned to undergo surgical treatment for benign prostatic hyperplasia. The 15 patients with a bladder contractility index less than 100 were assigned to the detrusor underactivity group while the 15 with a bladder contractility index more than 100 were assigned to the no detrusor underactivity group. Bladder mucosal specimens were collected at surgical prostate resection, and adenosine triphosphate and endothelial nitric oxide synthase were analyzed in these specimens. The levels of adenosine triphosphate and endothelial nitric oxide synthase were compared between the 2 groups. The correlation of urodynamic parameters with adenosine triphosphate and endothelial nitric oxide synthase was assessed in all patients.

RESULTS

Mean ± SEM endothelial nitric oxide synthase did not significantly differ between the detrusor underactivity and no underactivity groups (3.393 ± 0.969 vs 1.941 ± 0.377 IU/ml, p = 0.247). However, the mean level of adenosine triphosphate in the detrusor underactivity group was significantly lower than in the no detrusor underactivity group (1.289 ± 0.320 vs 9.262 ± 3.285 pmol, p = 0.011). In addition, in all patients adenosine triphosphate positively correlated with the bladder contractility index (r = 0.478, p = 0.018) and with detrusor pressure on maximal flow (r = 0.411, p = 0.046).

CONCLUSIONS

Adenosine triphosphate was significantly decreased in the urothelium in men with detrusor underactivity and benign prostatic hyperplasia, reflecting the change in detrusor function.

Effect of short-term androgen deficiency on bladder contractility and urothelial mediator release

In men, testosterone levels decline by 1% per year after the age of 40. Reduced androgen levels may directly contribute to lower urinary tract symptoms and bladder dysfunction, although the mechanisms are unclear. This study examined the effect of low testosterone and testosterone replacement on key mechanisms involved in local bladder function. Intraluminal release of the mediators ATP and ACh in response to bladder distension was measured in whole bladders from rats 8 weeks following castration, whilst bladder contractility was assessed using isolated strips. Human urothelial cells were cultured under low, physiological and supra-physiological testosterone conditions for 24 h or 5 days, and stretch-induced release of ATP and ACh was measured. Phasic contractile activity of bladder strips, agonist-induced reponses to carbachol and isoprenaline and nerve-evoked contractions were unaffected by castration. The acetylcholinesterase inhibitor neostigmine significantly increased amplitude of phasic activity only in bladder strips following castration, and this was prevented by testosterone replacement. Intraluminal ACh release following bladder distension was significantly reduced following castration, whilst ATP release was unaffected. In contrast, stretch-induced ATP release from urothelial cells was significantly enhanced in low testosterone conditions, whilst ACh release was unaltered. Testosterone-replacement to physiological levels prevented these changes. Whilst androgen deficiency of 8 weeks does not directly affect contractility of bladder smooth muscle, urothelial mediator release is sensitive to changes in testosterone. These changes in mediator release may be an early effect of the decline in testosterone and could affect sensory pathways in the longer term, contributing to the urinary symptoms and bladder dysfunction seen in androgen-deficient men.

ATP release from bladder urothelium and serosa in a rat model of partial bladder outlet obstruction

Overactive bladder is one of the major health problem especially in elderly people. Adenosine triphosphate (ATP) is released from urinary bladder cells and acts as a smooth muscle contraction and sensory signal in micturition but little is known about the role of ATP release in the pathophysiology of overactive bladder. To assess the relationship between ATP and overactive bladder, we used a partial bladder outlet obstruction (pBOO) model in rats. The bladder caused several changes by pBOO: An increase in bladder weight, hypertrophy of sub-urothelium and sub-serosal area, and frequent non-voiding bladder contraction during urine storage. Basal ATP release from urothelium and serosa of pBOO rats was significantly higher than that of normal rats. Distentioninduced ATP release from urothelium of normal and pBOO rats had no significant change. However, distention-induced ATP release from serosa of pBOO rats was higher than that of normal. These findings may identify ATP especially released from serosa as one of causes of non-voiding contractions and overactive bladder symptoms.

Increased Urinary Adenosine Triphosphate in Patients With Bladder Outlet Obstruction Due to Benign Prostate Hyperplasia

BACKGROUND

Diagnosis of bladder outflow obstruction (BOO) in patients with lower urinary tract (LUT) symptoms is challenging without using invasive urodynamic tests. Recently, we showed in vitro that urothelial strips from patients with benign prostatic hyperplasia (BPH) release more ATP than controls. Here, we tested whether urinary ATP can be used as a wall tension transducer non-invasive biomarker to detect BOO in patients with BPH.

METHODS

79 male patients with BOO and 22 asymptomatic controls were recruited prospectively. Patients were asked to complete the International Prostate Symptom Score (IPSS) questionnaire and to void at normal desire into a urinary flowmeter; the postvoid residual volume was determined by suprapubic ultrasonography. Urine samples from all individuals were examined for ATP, creatinine, and lactate dehydrogenase.

RESULTS

BOO patients had significantly higher (P < 0.001) urinary ATP normalized by the voided volume (456 ± 36 nmol) than age-matched controls (209 ± 35 nmol). Urinary ATP amounts increased with the voided volume, but the slope of this rise was higher in BOO patients than in controls. A negative correlation was detected between urinary ATP and flow rate parameters, namely maximal flow rate (r = -0.310, P = 0.005), Siroky flow-volume normalization (r = -0.324, P = 0.004), and volume-normalized flow rate index (r = -0.320, P = 0.012). We found no correlation with LUT symptoms IPSS score. Areas under the receiver operator characteristics (ROC) curves were 0.91 (95%CI 0.86-0.96, P < 0.001) for ATP alone and 0.88 (95%CI 0.81-0.94, P < 0,001) when adjusted to urinary creatinine.

CONCLUSIONS

Patients with BOO release higher amounts of ATP into the urine than the control group. The high area under the ROC curve suggests that urinary ATP can be a high-sensitive non-invasive biomarker of BOO, which may have a discriminative value of detrusor competence when comparing BPH patients with low urinary flow rates. Prostate 76:1353-1363, 2016. © 2016 Wiley Periodicals, Inc.

Urgency urinary incontinence and the interoceptive network: a functional magnetic resonance imaging study

BACKGROUND

Treatment of urgency urinary incontinence has focused on pharmacologically treating detrusor overactivity. Recent recognition that altered perception of internal stimuli (interoception) plays a role in urgency urinary incontinence suggests that exploration of abnormalities of brain function in this disorder could lead to better understanding of urgency incontinence and its treatment.

OBJECTIVE

We sought to: (1) evaluate the relationship between bladder filling, perceived urgency, and activation at brain sites within the interoceptive network in urgency urinary incontinence; (2) identify coactivation of other brain networks that could affect interoception during bladder filling in urgency incontinence; and (3) demonstrate interaction between these sites prior to bladder filling by evaluating their resting-state connectivity.

STUDY DESIGN

We performed an observational cohort study using functional magnetic resonance imaging to compare brain function in 53 women with urgency urinary incontinence and 20 controls. Whole-brain voxelwise analyses of covariance were performed to examine differences in functional brain activation between groups during a task consisting of bladder filling, hold (static volume), and withdrawal phases. The task was performed at 3 previously established levels of baseline bladder volume, the highest exceeding strong desire to void volume. All women continuously rated their urge on a 0- to 10-point Likert scale throughout the task and a mixed measures analysis of variance was used to test for differences in urge ratings. Empirically derived regions of interest from analysis of activation during the task were used as seeds for examining group differences in resting-state functional connectivity.

RESULTS

In both urgency urinary incontinent participants and controls, changes in urge ratings were greatest during bladder filling initiated from a high baseline bladder volume and urgency incontinent participants' rating changes were greater than controls. During this bladder-filling phase urgency incontinent participant's activation of the interoceptive network was greater than controls, including in the left insula and the anterior and middle cingulate cortex. Urgency incontinent participant's activation was also greater than controls at sites in the ventral attention network and posterior default mode network. Urgency incontinent participant's connectivity was greater than controls between a middle cingulate seed point and the dorsal attention network, a "top-down" attentional network. Control connectivity was greater between the midcingulate seed point and the ventral attention network, a "bottom-up" attentional network.

CONCLUSION

Increasing urge was associated with greater urgency incontinent participant than control activation of the interoceptive network and activation in networks that are determinants of self-awareness (default mode network) and of response to unexpected external stimuli (ventral attention network). Differences in connectivity between interoceptive networks and opposing attentional networks (ventral attention network vs dorsal attention network) were present even before bladder filling (in the resting state). These findings are strong evidence for a central nervous system component of urgency urinary incontinence that could be mediated by brain-directed therapies.

Purinergic signalling in the urinary bladder

It is well established that in most species, exocytotic vesicular release of ATP from parasympathetic neurons contributes to contraction of the bladder. However, ATP is released not only from parasympathetic nerves, but also from the urothelium. During bladder filling, the urothelium is stretched and ATP is released from the umbrella cells thereby activating mechanotransduction pathways. ATP release can also be induced by various mediators present in the urine and and/or released from nerves or other components of the lamina propria. Urothelial release of ATP is mainly attributable to vesicular transport or exocytosis and, to a smaller extent, to pannexin hemichannel conductive efflux. After release, ATP acts on P2X3 and P2X2/3 receptors on suburothelial sensory nerves to initiate the voiding reflex and to mediate the sensation of bladder filling and urgency. ATP also acts on suburothelial interstitial cells/myofibroblasts generating an inward Ca(2+) transient that via gap junctions could provide a mechanism for long-distance spread of signals from the urothelium to the detrusor muscle. ATP release can be affected by urological diseases, e.g., interstitial cystitis and both the mechanisms of release and the receptors activated by ATP may be targets for future drugs for treatment of lower urinary tract disorders.