Damage to the bladder neck alters autonomous activity and its sensitivity to cholinergic agonists

Urodynamic effects of prostatic urethral lift procedure for male voiding LUTS

AIMS

Primary objective is to investigate whether prostatic urethral lift (PUL) results in an improvement of urodynamic parameters that define bladder outlet obstruction (urethral resistance algorithm [URA], Schäfer grade, PdetQmax, PdetOpen).

METHODS

20 patients (main inclusion criteria: ≥ 50 years of age, BPO, IPSS ≥ 13, prostate volume ≤ 60 mL, no middle prostate lobe) were enrolled in the study and a PUL was performed. Patients underwent urodynamic investigation and filled out the IPSS and QoL before and after PUL. A paired T test was used to analyze the results.

RESULTS

The mean age was 68 years (range 55-79), mean prostate volume (TRUS) was 45 mL (range 20-59) and mean PSA was 2.0 ug/L (0.2-4.4). IPSS of the 16 patients reduced significantly (from 22.20 to 14.47, p=0.000). Qmax during pressure flow study improved significantly (from 4.5 ml/s to 7.2 ml/s, p=0.001), no significant difference was found in Qmax during free uroflowmetry. There was no significant difference found in post voiding residual. URA decreased significantly post treatment (from 52 cmH2O to 37 cmH2O, p=0.000). The Schäfer obstruction plot decreased significantly (from 3.5 to 2.6, p= 0.022). Seven patients underwent Greenlight Laser Vaporization of the prostate after the PUL due to unsatisfactory results.

CONCLUSIONS

PUL has desobstructive effects, but they seem clinically modest. The procedure improves urodynamic parameters as well as QoL in males with LUTS based on BPO. However, the mechanism how PUL leads to a remarkable symptom relieve remains unclear and cannot be explained by the desobstructive mechanisms we observed.

Effects of High Salt Intake on Detrusor Muscle Contraction in Dahl Salt-Sensitive Rats

High salt intake has been reported as a risk factor for urinary storage symptoms. However, the association between high salt intake and detrusor muscle contraction is not clear. Therefore, we investigated the effects of high salt intake on the components of detrusor muscle contraction in rats. Six-week-old male Dahl salt-resistant (DR; n = 5) and Dahl salt-sensitive (DS; n = 5) rats were fed a high salt (8% NaCl) diet for one week. The contractile responses of the detrusor muscle to the cumulative administration of carbachol and electrical field stimulation (EFS) with and without suramin and atropine were evaluated via isometric tension study. The concentration-response curves of carbachol were shifted more to the left in the DS group than those in the DR group. Contractile responses to EFS were more enhanced in the DS group than those in the DR group (p < 0.05). Cholinergic component-induced responses were more enhanced in the DS group than those in the DR group (p < 0.05). High salt intake might cause urinary storage symptoms via abnormalities in detrusor muscle contraction and the enhancement of cholinergic signals. Excessive salt intake should be avoided to preserve bladder function.

Urethral meatus stricture BOO stimulates bladder smooth muscle cell proliferation and pyroptosis via IL‑1β and the SGK1‑NFAT2 signaling pathway

Bladder outlet obstruction (BOO), which is primarily caused by benign prostatic hyperplasia, is a common chronic disease. However, previous studies have most commonly investigated BOO using the acute obstruction model. In the present study, a chronic obstruction model was established to investigate the different pathological alterations in the bladder between acute and chronic obstruction. Compared with chronic obstruction, acute obstruction led to increased expression of proliferating cell nuclear antigen and interleukin-1β, which are markers of proliferation and inflammation, respectively. Furthermore, increased fibrosis in the bladder at week 2 was observed. Low pressure promoted mice bladder smooth muscle cell (MBSMC) proliferation, and pressure overload inhibited cell proliferation and increased the proportion of dead MBSMCs. Further investigation using serum/glucocorticoid regulated kinase 1 (SGK1) small interfering RNAs indicated that low pressure may promote MBSMC proliferation by upregulating SGK1 and nuclear factor of activated T-cell expression levels. Therefore, the present study suggested that acute obstruction led to faster decompensation of bladder function and chronic bladder obstruction displayed an enhanced ability to progress to BOO.

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

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

Impact of a folic acid-enriched diet on urinary tract function in mice treated with testosterone and estradiol

Aging men are susceptible to developing lower urinary tract symptoms, but the underlying etiology is unknown and the influence of dietary and environmental factors on them is unclear. We tested whether a folic acid-enriched diet changed urinary tract physiology and biology in control male mice and male mice with urinary dysfunction induced by exogenous testosterone and estradiol (T+E2), which mimics changing hormone levels in aging humans. T+E2 treatment increased mouse urine output, time between voiding events, and bladder capacity and compliance. Consumption of a folic acid-enriched diet moderated these changes without decreasing prostate wet weight or threshold voiding pressure. One potential mechanism for these changes involves water balance. T+E2 treatment increases plasma concentrations of anti-diuretic hormone, which is offset at least in part by a folic acid-enriched diet. Another potential mechanism involves neural control of micturition. The folic acid-enriched diet, fed to T+E2-treated mice, increased voiding frequency in response to intravesicular capsaicin infusion and increased mRNA abundance of the capsaicin-sensitive cation channel transient receptor potential vanilloid subfamily member 1 (Trpv1) in L6 and S1 dorsal root ganglia (DRG) neurons. T+E2 treatment and a folic acid-enriched diet also modified DNA methylation, which is capable of altering gene expression. We found the enriched diet increased global DNA methylation in dorsal and ventral prostate and L6 and S1 DRG. Our results are consistent with folic acid acting to slow or reverse T+E2-mediated alteration in urinary function in part by normalizing water balance and enhancing or preserving afferent neuronal function.

Overactive bladder syndrome and the potential role of prostaglandins and phosphodiesterases: an introduction

In this paper, a general introduction is given, presenting the overactive bladder syndrome (OAB) and its impact on the quality of life and economical burden in patients affected. Moreover, the anatomy, physiology and histology of the lower urinary tract are discussed, followed by a brief overview on the possible role of prostaglandin (PG) and phosphodiesterase type 5 (PDE5) in the urinary bladder. The current literature on the role and distribution of PGE2 and its receptors in the urinary bladder is discussed. In both animal models and in human studies, high levels of signaling molecules such as PG and cGMP have been implicated, in decreased functional bladder capacity and micturition volume, as well as in increased voiding contraction amplitude. As a consequence, inhibition of prostanoid production, the use of prostanoid receptor antagonists, or PDE inhibitors might be a rational way to treat patients with detrusor overactivity. Similarly, prostanoid receptor agonists, or agents that stimulate their production, might have a function in treating bladder underactivity.

The effect of indomethacin on the muscarinic induced contractions in the isolated normal guinea pig urinary bladder

Background

To investigate the effect of prostaglandin depletion by means of COX-inhibition on cholinergic enhanced spontaneous contractions.

Methods

The urethra and bladder of 9 male guinea pigs (weight 270–300 g) were removed and placed in an organ bath with Krebs’ solution. A catheter was passed through the urethra through which the intravesical pressure was measured. The muscarinic agonist arecaidine, the non-selective COX inhibitor indomethacin, and PGE₂ were subsequently added to the organ bath. The initial average frequency and amplitude of spontaneous contractions in the first 2 minutes after arecaidine application were labelled F_ini and P_ini, respectively. The steady state frequency (F_steady) and amplitude (P_steady) were defined as the average frequency and amplitude during the 5 minutes before the next wash out.

Results

Application of 1 μM PGE₂ increased the amplitude of spontaneous contractions without affecting frequency. 10 μM of indomethacin reduced amplitude but not frequency.

The addition of indomethacin did not alter F_ini after the first application (p = 0.7665). However, after the second wash, F_ini was decreased (p = 0.0005). F_steady, P_steady and P_ini were not significantly different in any of the conditions. These effects of indomethacin were reversible by PGE₂ addition._.

Conclusions

Blocking PG synthesis decreased the cholinergically stimulated autonomous contractions in the isolated bladder. This suggests that PG could modify normal cholinergically evoked response. A combination of drugs inhibiting muscarinic receptors and PG function or production can then become an interesting focus of research on a treatment for overactive bladder syndrome.

From urothelial signalling to experiencing a sensation related to the urinary bladder

The mechanisms underlying bladder sensation and the way we experience sensations during normal voiding and in pathology is complex and not well understood. During storage and emptying, mechanical changes occurring in number of cell types within the bladder wall (i.e. the uroepithelium and bladder afferents) can have a major influence on our sensory systems. In this review, we discuss bladder sensation with a focus on coding events in the periphery.

Modulation of non-voiding activity by the muscarinergic antagonist tolterodine and the β(3)-adrenoceptor agonist mirabegron in conscious rats with partial outflow obstruction

Experimental urethral obstruction in rats alters micturition patterns with non-voiding activity (NVA) during filling cystometry, showing similarity to that observed in human detrusor overactivity. Several drug classes with therapeutic potential in overactive bladder in humans have been tested in this model in rats, rabbits or guinea pigs, but no detailed analysis of drug effects on cystometric patterns has been published. The present study uses a rat model of overactivity with partial bladder outflow obstruction (BOO) in combination with the procedures to analyse NVA to study the effects of the anticholinergic drug tolterodine and the novel β(3)-adrenoceptor agonist mirabegron. The current data for the first time show that NVA in rats with BOO is sensitive to both the muscarinergic antagonist tolterodine and the β(3)-adrenoceptor agonist mirabegron, but with clear differences between the two drugs: during progression of bladder filling, tolterodine affected both the amplitude and frequency of NVA whereas mirabegron affected primarily the frequency. In addition, tolterodine dose-dependently reduced voiding contractions, while mirabegron did not. A model is proposed to account for these observations where both agents act on a 'pacemaker-like' mechanism which is sensitive to cholinergic excitatory and beta-adrenergic inhibitory inputs. Such concepts could provide insights into the nature of overactive bladder and the site of action of key therapeutic drugs.

OBJECTIVE

To investigate the hypothesis that tolterodine and the β(3)-adrenoceptor agonist mirabegron exert their actions on the motor component of the motor/sensory system in the bladder wall: non-voiding activity (NVA).

MATERIALS AND METHODS

The present study used standard cystometric techniques and a conscious rat model of partial bladder outflow obstruction (BOO). A single dose of either tolterodine (0.01, 0.1 0.3 or 1.0 mg/kg) or mirabegron (0.03, 0.1, 0.3, 1.0 or 3.0 mg/kg) was given i.v. to each animal.

RESULTS

In the dose ranges used, tolterodine reduced the voiding contraction amplitude, whereas mirabegron did not. Non-voiding activity consisted of small (<0.6 mmHg) and large (>0.6 mmHg) transients. As a fill progressed, both tolterodine and mirabegron reduced the cumulative activity of the large non-voiding contractions, but had little effect on the small transients. Tolterodine affected both the amplitude and frequency of NVA, whereas mirabegron affected primarily the frequency.

CONCLUSIONS

Non-voiding activity is sensitive to muscarinergic antagonists and β(3)-adrenoceptor agonists, but there are clear differences between the two drugs. A model is proposed to account for these observations where both agents act on a 'pacemaker-like' mechanism with cholinergic excitatory and adrenergic inhibitory inputs. Such concepts may provide insights into the nature of overactive bladder and the site of action of key therapeutic drugs.

Interactions between cholinergic and prostaglandin signaling elements in the urothelium: role for muscarinic type 2 receptors

OBJECTIVE

To characterize the interactions between the cholinergic and prostaglandin signaling systems within the urothelium-lamina propria of the guinea pig and elucidate the role of muscarinic receptors in these interactions.

METHODS

The urothelium-lamina propria was isolated from guinea pig bladders, cut into strips (5×10 mm), and maintained in vitro. The tissue was either stretched or left unstretched but exposed to 2'(3')-O-(4-benzoylbenzoyl)adenosine-5'-triphosphate tri(triethylammonium) salt, arecaidine, and prostaglandin E2 (PGE2). Acetylcholine and PGE2 release was measured using a GeneBLAzer M3 CHO-K1-bla cell reporter assay and an enzyme immunoassay, respectively. The role of the muscarinic type 2 and 3 (M2 and M3, respectively) receptors and nitric oxide in mediating PGE2 release was determined in the presence of the muscarinic antagonists 11-[(2-[(diethylamino)methyl]-1-piperidinyl)acetyl]-5,11-dihydro-6H-pyrido[2,3b][1,4] benzodiazepin-6-one and darafenicin and a nitric oxide donor (NONOate).

RESULTS

Acetylcholine release was detected in response to stretch and in the unstretched preparations exposed to PGE2 or the adenosine triphosphate analog 2'(3')-O-(4-benzoylbenzoyl)adenosine-5'-triphosphate tri(triethylammonium) salt. The cholinergic agonist arecaidine induced a concentration-dependent production of PGE2 (half-maximal concentration 75 nM). The arecaidine stimulation of PGE2 production was inhibited in a dose-dependent manner by the antagonist AFDX-116 (M2>M3; half-maximal inhibition 110 nM) but not darifenacin (M3>>M2). Finally, in the presence of the nitric oxide donor, NONOate, arecaidine-stimulated PGE2 production was inhibited.

CONCLUSION

These observations demonstrate that complex signal interactions occur within the urothelium involving acetylcholine, adenosine triphosphate, nitric oxide, and PGE2. In addition, the data have demonstrated a role for muscarinic M2 receptors and nitric oxide in the cholinergic regulation of PGE2 production in the bladder wall.

M3 muscarinic receptor-like immunoreactivity in sham operated and obstructed guinea pig bladders

PURPOSE

Type 3 muscarinic receptors, which are present in the bladder wall, are important for bladder function. However, their role in the context of the urothelium is not well defined. Understanding the role of type 3 muscarinic receptors has been limited by the lack of specific type 3 muscarinic receptor antibodies. Thus, we identified a specific type 3 muscarinic receptor antibody and investigated the site of type 3 muscarinic receptors in sham operated and obstructed guinea pig bladders.

MATERIALS AND METHODS

The specificity of 4 commercially available type 3 muscarinic receptor antibodies was determined. Immunohistochemistry was then done in bladder tissue from sham operated and obstructed guinea pig bladders.

RESULTS

One of the 4 antibodies examined had the needed specificity in terms of blocking peptide and Western blot characterization. Using this antibody type 3 muscarinic receptor immunoreactivity was associated with muscle cells, nerves and interstitial cells. Four types of interstitial cells were identified, including suburothelial, lamina propria, surface muscle and intramuscular interstitial cells. In the obstructed model the bladder wall was hypertrophied and there was nerve fiber loss. The number of lamina propria, surface muscle and intramuscular interstitial cells was increased but not the number of suburothelial interstitial cells. Also, surface muscle interstitial cells appeared to form clusters or nodes with type 3 muscarinic receptor immunoreactivity.

CONCLUSIONS

Nerve loss and the up-regulation of interstitial cells with type 3 muscarinic receptor immunoreactivity may underlie major functional changes in the pathological bladder. This indicates that type 3 muscarinic receptor specific anticholinergic drugs may affect not only the detrusor muscle, as previously thought, but also interstitial cells and nerve fibers.

Neural control of the lower urinary tract: peripheral and spinal mechanisms

This review deals with individual components regulating the neural control of the urinary bladder. This article will focus on factors and processes involved in the two modes of operation of the bladder: storage and elimination. Topics included in this review include: (1) The urothelium and its roles in sensor and transducer functions including interactions with other cell types within the bladder wall ("sensory web"), (2) The location and properties of bladder afferents including factors involved in regulating afferent sensitization, (3) The neural control of the pelvic floor muscle and pharmacology of urethral and anal sphincters (focusing on monoamine pathways), (4) Efferent pathways to the urinary bladder, and (5) Abnormalities in bladder function including mechanisms underlying comorbid disorders associated with bladder pain syndrome and incontinence.

Partial bladder outlet obstruction reduces the tissue antioxidant capacity and muscle nerve density of the guinea pig bladder

AIMS

Reactive nitrogen and oxygen species (RNOS) likely play a role in the development of bladder dysfunction related to bladder outlet obstruction. Antioxidants protect against these free radicals. The aim of our study was to investigate the effect of bladder outlet obstruction on the endogenous antioxidant status of the bladder and to correlate this to bladder structure and function.

METHODS

In 16 guinea pigs either a partial outlet obstruction or a sham operation was induced. The contractile responses of detrusor strips to electrical field stimulation (EFS), acetylcholine, potassium, and ATP were monitored 4 weeks after the operation. The nerve density in bladder tissue was determined by using the non-specific nerve marker PGP 9.5. Separate antioxidants and the total antioxidant status were assessed using the trolox equivalent antioxidant capacity (TEAC) test.

RESULTS

Contractile responses of detrusor strips to EFS were for the greater part based on neurogenic stimulation. The nerve-mediated responses in strips from obstructed bladders were lower compared to the sham group. Obstructed bladders showed a patchy denervation and the nerve density was significantly lower compared to the sham group. The total antioxidant capacity, the glutathione and the glutathione reductase (GR) levels significantly decreased in obstructed bladders compared to the sham group.

CONCLUSION

This study demonstrates that the antioxidant status of guinea pig bladders exposed to outlet obstruction decreased which might be associated with the observed reduction in nerve density. The results strengthen the hypothesis that oxidative stress is involved in the pathophysiology of bladder dysfunction related to obstructed bladders. Neurourol. Urodynam. 28:461-467, 2009. (c) 2008 Wiley-Liss, Inc.

Spontaneous release of acetylcholine from autonomic nerves in the bladder

BACKGROUND AND PURPOSE

Bladder contractility is regulated by intrinsic myogenic mechanisms interacting with autonomic nerves. In this study, we have investigated the physiological role of spontaneous release of acetylcholine in guinea pig and rat bladders.

EXPERIMENTAL APPROACH

Conventional isotonic or pressure transducers were used to record contractile activity of guinea pig and rat bladders.

KEY RESULTS

Hyoscine (3 micromol x L(-1)), but not tetrodotoxin (TTX, 1 micromol x L(-1)), reduced basal tension, distension-evoked contractile activity and physostigmine (1 micromol x L(-1))-evoked contractions of the whole guinea pig bladder and muscle strips in vitro. omega-Conotoxin GVIA (0.3 micromol x L(-1)) did not affect physostigmine-induced contractions when given either alone or in combination with omega-agatoxin IVA (0.1 micromol x L(-1)) and SNX 482 (0.3 micromol x L(-1)). After 5 days in organotypic culture, when extrinsic nerves had significantly degenerated, the ability of physostigmine to induce contractions was reduced in the dorso-medial strips, but not in lateral strips (which have around 15 times more intramural neurones). Most muscle strips from adult rats lacked intramural neurones. After 5 days in culture, physostigmine-induced or electrical field stimulation-induced contractions of the rat bladder strips were greatly reduced. In anaesthetized rats, topical application of physostigmine (5-500 nmol) on the bladder produced a TTX-resistant tonic contraction that was abolished by atropine (4.4 micromol x kg(-1) i.v.).

CONCLUSIONS AND IMPLICATIONS

The data indicate that there is spontaneous TTX-resistant release of acetylcholine from autonomic cholinergic extrinsic and intrinsic nerves, which significantly affects bladder contractility. This release is resistant to blockade of N, P/Q and R type Ca(2+) channels.

Ubiquitin hydrolase (protein gene product 9.5) in the obstructed bladder: evidence for tissue remodelling involving a subset of interstitial cells

OBJECTIVE

To examine the expression of ubiquitin hydrolase (UH), an enzyme which is part of the ubiquitin-proteasome system involved in the regulation of cell growth and differentiation, to gain an insight into the cell types and processes underlying the tissue remodelling that occur after bladder neck damage.

MATERIALS AND METHODS

Three groups of male guinea pigs were used, comprising controls (not operated, four), sham (five) and obstructed (six). The bladder outlet was obstructed by implanting a silver ring around the urethra, which was left in situ for 2-4 weeks. Sham-operated guinea pigs had the same operative procedure but no ring was implanted. The bladders were removed and incubated in Krebs' solution at 36 degrees C, gassed with 95% O2 and 5% CO2, Tissues were then fixed in 4% depolymerized paraformaldehyde and processed for immunohistochemistry. We used antibodies raised against UH, cyclooxygenase type I and vimentin. Specific antibody binding was visualized using the appropriate secondary antibodies.

RESULTS

Staining with an antibody to UH showed the presence of both sensory and motor nerves in control, sham and obstructed bladders. In the control bladders this was the predominant staining pattern. In the sham and obstructed bladders UH staining revealed additional positive cell types; cells associated with the outermost layers of the urothelium (the umbrella cells), in the lamina propria (the lamina propria interstitial cells (lp-ICs), on the surface of the muscle bundles (surface muscle, sm-ICs) and on the serosal surface (muscle coat, mc-ICs). All ICs stained with vimentin. The ICs within the muscle bundles (intramuscular, im-ICs) did not stain with UH. The number and density of the UH-positive cells was greater in the obstructed than in the sham bladders, suggesting a change in relation to the severity of damage to the bladder neck.

CONCLUSION

The expression of UH implies the re-targeting of proteins marked for degradation in the proteasome. Increased expression of UH in the lp-ICs and sm-ICs shows that these cells are active in the early and late stages of the tissue remodelling resulting from obstruction. These results show a further subset of ICs that might be involved in the increased deposition of extracellular material and tissue remodelling.

Regional differences in sensory innervation and suburothelial interstitial cells in the bladder neck and urethra

OBJECTIVE

To identify and characterize possible structural specialisations in the wall of the lower urinary tract (LUT) in the region of the bladder urethral junction (BUJ), with the specific objective of identifying regional variations in sensory nerve fibres and interstitial cells (ICs).

MATERIALS AND METHODS

The bladder base and urethra was removed from five male guinea pigs killed by cervical dislocation. Tissue pieces were incubated in Krebs' solution at 36 degrees C, gassed with 95% O(2) and 5% CO(2), fixed in 4% paraformaldehyde and processed for immunohistochemistry. The nonspecific marker vimentin and the general neuronal marker protein gene product (PGP) 9.5 were used to identify ICs and nerve fibres, respectively. Specific antibody binding was visualized using the appropriate secondary antibodies.

RESULTS

The wall of the LUT in the region immediately between the bladder base and the urethra, the BUJ, differed in its cellular composition relative to the adjacent areas. PGP-positive (PGP(+)) nerve fibres, presumptive afferent fibres, lay within the urothelium running between the epithelial cells. There were two general nerve patterns: branching fibres with no varicosities, and complex fibres with varicosities. Fibre collaterals with varicosities exited the urothelium and occupied the space under the urothelium adjacent to the layer of suburothelial ICs. The latter, lamina propria and around the muscle bundles were identified using vimentin (vim(+)). In the base a few vim(+) cells were also PGP(+). In the region of the BUJ there was a decrease in the amount of smooth muscle. In this region, below the lamina propria, there was an area densely populated with vim(+)/PGP(+) ICs. Nerve fibres ran between the cells in this region.

CONCLUSION

These structural specialisations within the urothelium and deeper layers of the BUJ suggest that they might be associated with specific functions. The localized highly branched network of the putative afferent nerves suggests the presence of a local axonal reflexes involving possible cross-talk between the urothelium and suburothelial layer. The function of the specialized region of ICs is not known and must await further information on the functional properties of this novel cell type. These observations show further the cellular heterogeneity of the cells in the LUT and the complexity of the structures. One of the major current challenges in functional urology is to understand the relationships between these novel structures and overall bladder and urethral function.