M2 and M3 muscarinic receptor activation of urinary bladder contractile signal transduction. II. Denervated rat bladder

Can Urinary Bladder Innervation Be Restored After Outlet Obstruction and Denervation?

Transurethral resection of the prostate, or other methods to decrease outlet resistance usually leads to relief of symptoms in patients with bladder outlet obstruction (BOO). If symptoms of underactivity persist after normalization of outflow conditions, treatment options are limited. In this review, we hypothesize, based on results from basic research, what might become treatment options for such patients in the future. The primary local treatment will still aim at reducing outlet obstruction. We speculate that local secondary treatment in the future might include transplantation of stem cells or mature bladder ganglion cells into the bladder wall. There has been some success in transplanting ganglion cells into the rat bladder. The ganglion cells will sprout into the surrounding tissue but functional connections between the axons of the transplanted neurons, and the detrusor smooth muscle have so far not been demonstrated. Neurotrophins or neurotrimin might be injected into the bladder wall to increase the sprouting of existing or transplanted neurons. Stem cell transplantation has been performed and improves detrusor function, but it has so far, been difficult to demonstrate transplanted stem cells. BOO, persisting detrusor underactivity, and decreased nerve density are often combined with inflammatory activity of the lower urinary tract. NLR family pyrin domain containing 3 (NLRP3) and its messenger RNA (mRNA) as well as cyclooxygenase-2 (Cox-2) mRNA are increased in obstructed bladders. Systemic treatment with the NLRP3 inhibitor glyburide normalized nerve density in rat bladder, and, to some extent, bladder function. It is unclear whether Cox-2 is involved in the decreased nerve density following obstruction, but Cox-2 mRNA increases 5-fold in obstructed bladder. Future therapy against bladder underactivity remaining following relief of obstruction includes either systemic treatment, perhaps by anti-inflammatory drugs, or local treatment by injection of stem cells, mature ganglion cells, and/or neurotrophins or neurotrimin into the bladder wall.

Intracellular signaling pathways of muscarinic acetylcholine receptor-mediated detrusor muscle contractions

Acetylcholine plays an essential role in the regulation of detrusor muscle contractions, and antimuscarinics are widely used in the management of overactive bladder syndrome. However, several adverse effects limit their application and patients' compliance. Thus, this study aimed to further analyze the signal transduction of M2 and M3 receptors in the murine urinary bladder to eventually find more specific therapeutic targets. Experiments were performed on adult male wild-type, M2, M3, M2/M3, or Gαq/11 knockout (KO), and pertussis toxin (PTX)-treated mice. Contraction force and RhoA activity were measured in the urinary bladder smooth muscle (UBSM). Our results indicate that carbamoylcholine (CCh)-induced contractions were associated with increased activity of RhoA and were reduced in the presence of the Rho-associated kinase (ROCK) inhibitor Y-27632 in UBSM. CCh-evoked contractile responses and RhoA activation were markedly reduced in detrusor strips lacking either M2 or M3 receptors and abolished in M2/M3 KO mice. Inhibition of Gαi-coupled signaling by PTX treatment shifted the concentration-response curve of CCh to the right and diminished RhoA activation. CCh-induced contractile responses were markedly decreased in Gαq/11 KO mice; however, RhoA activation was unaffected. In conclusion, cholinergic detrusor contraction and RhoA activation are mediated by both M2 and M3 receptors. Furthermore, whereas both Gαi and Gαq/11 proteins mediate UBSM contraction, the activation at the RhoA-ROCK pathway appears to be linked specifically to Gαi. These findings may aid the identification of more specific therapeutic targets for bladder dysfunctions.NEW & NOTEWORTHY Muscarinic acetylcholine receptors are of utmost importance in physiological regulation of micturition and also in the development of voiding disorders. We demonstrate that the RhoA-Rho-associated kinase (ROCK) pathway plays a crucial role in contractions induced by cholinergic stimulation in detrusor muscle. Activation of RhoA is mediated by both M2 and M3 receptors as well as by Gi but not Gq/11 proteins. The Gi-RhoA-ROCK pathway may provide a novel therapeutic target for overactive voiding disorders.

[Conservative and pharmacological treatment of benign prostatic hyperplasia : The German S2e-guideline 2023-part2]

BACKGROUND

Lower urinary tract symptoms (LUTS) suggestive of benign prostatic hyperplasia (BPH, in German guidelines: benign prostatic syndrome [BPS]) is considered the most common disease of the lower urinary tract in men and can have a tremendous impact on the quality-of-life of affected patients. Conservative and pharmacological therapy of this disease are of great importance, both in improving LUTS and reducing progression-related complications.

OBJECTIVES

Presentation of the conservative and pharmacological treatment options according to the current German S2e guideline on BPS.

MATERIALS AND METHODS

Summary and overview of chapters 9 and 10 of the current German S2e guideline on BPS.

RESULTS

In addition to a controlled watchful waiting for BPS patients without an absolute indication for prostate surgery, a variety of phytopharmacological formulations and synthetic drugs according to the symptomatology and clinical progress are available. Phytotherapy should, due to inconsistent study data, only be considered for mild to moderate symptoms. Synthetic drugs include alpha-blockers, 5α-reductase inhibitors, phosphodiesterase inhibitors, antimuscarinics and, more recently, the β3-agonist mirabegron in the current guideline. In addition, various combination therapies are listed and evaluated according to their indications, effects and side effects.

CONCLUSIONS

The current German S2e guideline on the diagnosis and treatment of BPS provides an evidence-based foundation for finding the best possible and most effective medication.

Current and Emerging Pharmacological Targets and Treatments of Urinary Incontinence and Related Disorders

Overactive bladder syndrome with and without urinary incontinence and related conditions, signs, and disorders such as detrusor overactivity, neurogenic lower urinary tract dysfunction, underactive bladder, stress urinary incontinence, and nocturia are common in the general population and have a major impact on the quality of life of the affected patients and their partners. Based on the deliberations of the subcommittee on pharmacological treatments of the 7th International Consultation on Incontinence, we present a comprehensive review of established drug targets in the treatment of overactive bladder syndrome and the aforementioned related conditions and the approved drugs used in its treatment. Investigational drug targets and compounds are also reviewed. We conclude that, despite a range of available medical treatment options, a considerable medical need continues to exist. This is largely because the existing treatments are symptomatic and have limited efficacy and/or tolerability, which leads to poor long-term adherence. SIGNIFICANCE STATEMENT: Urinary incontinence and related disorders are prevalent in the general population. While many treatments have been approved, few patients stay on long-term treatment despite none of them being curative. This paper provides a comprehensive discussion of existing and emerging treatment options for various types of incontinence and related disorders.

Anticholinergics combined with alpha-blockers for treating lower urinary tract symptoms related to benign prostatic obstruction

BACKGROUND

Lower urinary tract symptoms (LUTS) due to benign prostatic obstruction (BPO) represent one of the most common clinical complaints in men. Alpha-blockers are widely used as first-line therapy for men with LUTS secondary to BPO, but up to one third of men report no improvement in their LUTS after taking alpha-blockers. Anticholinergics used in addition to alpha-blockers may help improve symptoms but it is uncertain how effective they are.  OBJECTIVES: To assess the effects of combination therapy with anticholinergics and alpha-blockers in men with LUTS related to BPO.

SEARCH METHODS

We performed a comprehensive search of medical literature, including the Cochrane Library, MEDLINE, Embase, and trials registries, with no restrictions on the language of publication or publication status. The date of the latest search was 7 August 2020.

SELECTION CRITERIA

We included randomized controlled trials. Inclusion criteria were men with LUTS secondary to BPO, ages 40 years or older, and a total International Prostate Symptom Score of 8 or greater. We excluded trials of men with a known neurogenic bladder due to spinal cord injury, multiple sclerosis, or central nervous system disease, and those examining medical therapy for men who were treated with surgery for BPO. We performed three comparisons: combination therapy versus placebo, combination therapy versus alpha-blockers monotherapy, and combination therapy versus anticholinergics monotherapy.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened the literature, extracted data, and assessed risk of bias. We performed statistical analyses using a random-effects model and interpreted data according to the Cochrane Handbook for Systematic Reviews of Interventions. We used the GRADE approach to rate the certainty of evidence.

MAIN RESULTS

We included 23 studies with 6285 randomized men across three comparisons. The mean age of participants ranged from 54.4 years to 73.9 years (overall mean age 65.7 years). Of the included studies, 12 were conducted with a single-center setting, while 11 used a multi-center setting. We only found short-term effect (12 weeks to 12 months) of combination therapy based on available evidence. Combination therapy versus placebo: based on five studies with 2369 randomized participants, combination therapy may result in little or no difference in urologic symptom scores (mean difference (MD) -2.73, 95% confidence interval (CI) -5.55 to 0.08; low-certainty evidence). We are very uncertain about the effect of combination therapy on quality of life (QoL) (MD -0.97, 95% CI -2.11 to 0.16; very low-certainty evidence). Combination therapy likely increases adverse events (risk ratio (RR) 1.24, 95% CI 1.04 to 1.47; moderate-certainty evidence); based on 252 adverse events per 1000 participants in the placebo group, this corresponds to 61 more adverse events (95% CI 10 more  to 119 more) per 1000 participants treated with combination therapy. Combination therapy versus alpha-blockers alone: based on 22 studies with 4904 randomized participants, we are very uncertain about the effect of combination therapy on urologic symptom scores (MD -2.04, 95% CI -3.56 to -0.52; very low-certainty evidence) and QoL (MD -0.71, 95% CI -1.03 to -0.38; very low-certainty evidence). Combination therapy may result in little or no difference in adverse events rate (RR 1.10, 95% CI 0.90 to 1.34; low-certainty evidence); based on 228 adverse events per 1000 participants in the alpha-blocker group, this corresponds to 23 more adverse events (95% CI 23 fewer to 78 more) per 1000 participants treated with combination therapy. Combination therapy compared to anticholinergics alone: based on three studies with 1218 randomized participants, we are very uncertain about the effect of combination therapy on urologic symptom scores (MD -3.71, 95% CI -9.41 to 1.98; very low-certainty evidence). Combination therapy may result in an improvement in QoL (MD -1.49, 95% CI -1.88 to -1.11; low-certainty evidence). Combination therapy likely results in little to no difference in adverse events (RR 1.26, 95% CI 0.81 to 1.95; moderate-certainty evidence); based on 115 adverse events per 1000 participants in the anticholinergic alone group, this corresponds to 4 fewer adverse events (95% CI 7 fewer to 13 more) per 1000 participants treated with combination therapy.

AUTHORS' CONCLUSIONS

Based on the findings of the review, combination therapy with anticholinergics and alpha-blockers are associated with little or uncertain effects on urologic symptom scores compared to placebo, alpha-blockers, or anticholinergics monotherapy. However, combination therapy may result in an improvement in quality of life compared to anticholinergics monotherapy, but an uncertain effect compared to placebo, or alpha-blockers. Combination therapy likely increases adverse events compared to placebo, but not compared to alpha-blockers or anticholinergics monotherapy. The findings of this review were limited by study limitations, inconsistency, and imprecision. We were unable to conduct any of the predefined subgroup analyses.

Excitatory effect of acotiamide on rat and human bladder: Implications for underactive bladder treatment

OBJECTIVE

To evaluate whether approved gastroprokinetic agent, acotiamide exerts a direct excitatory effect on bladder to help explain the reported meaningful reduction of post-void residual urine volume (PVR) in detrusor underactivity (DU) patients after thrice daily oral intake of acotiamide 100 mg for 2 weeks.

METHODS

Effect of acotiamide [1-16 μM] was assessed on nerve-mediated contractions evoked by electrical field stimulation (EFS) for 5 s with 5 ms pulse trains of 10 V in longitudinal, mucosa intact rat and human bladder strips to construct frequency response curve (1-32 Hz) and repeat 10 Hz stimulation at 60s interval. Effect of acotiamide 2 μM on spontaneous and carbachol evoked contractions was also assessed.

RESULTS

Acotiamide 2 μM significantly enhanced the Atropine and Tetrodotoxin (TTX)-sensitive EFS evoked contractions of rat and human bladder at 8-32 Hz (Two-way ANOVA followed Sidak's multiple comparison; *p < 0.01) and on repeat 10 Hz stimulation (Paired Student's t-test; *p < 0.05), while producing a modest effect on the spontaneous contractions and a negligible effect on the carbachol evoked contractions.

CONCLUSIONS

Enhancement of TTX-sensitive evoked contractions of rat and human bladder by acotiamide is consistent with the enhancement of excitatory neuro-effector transmission mainly through prejunctional mechanisms. Findings highlight immense therapeutic potential of antimuscarinics with low M3 receptor affinity like acotiamide in Underactive bladder (UAB)/DU treatment.

Active acetylcholine receptors prevent the atrophy of skeletal muscles and favor reinnervation

Denervation of skeletal muscles induces severe muscle atrophy, which is preceded by cellular alterations such as increased plasma membrane permeability, reduced resting membrane potential and accelerated protein catabolism. The factors that induce these changes remain unknown. Conversely, functional recovery following denervation depends on successful reinnervation. Here, we show that activation of nicotinic acetylcholine receptors (nAChRs) by quantal release of acetylcholine (ACh) from motoneurons is sufficient to prevent changes induced by denervation. Using in vitro assays, ACh and non-hydrolysable ACh analogs repressed the expression of connexin43 and connexin45 hemichannels, which promote muscle atrophy. In co-culture studies, connexin43/45 hemichannel knockout or knockdown increased innervation of muscle fibers by dorsal root ganglion neurons. Our results show that ACh released by motoneurons exerts a hitherto unknown function independent of myofiber contraction. nAChRs and connexin hemichannels are potential molecular targets for therapeutic intervention in a variety of pathological conditions with reduced synaptic neuromuscular transmission.

Denervation of muscle fibres induces muscle atrophy, via mechanisms that remain unclear. Here, the authors show that binding of acetylcoline to its receptor at the neuromuscular junction represses the expression of connexins 43 and 45, which promote atrophy, and is sufficient to prevent denervation-induced loss of myofibre mass.

Simulated vaginal delivery causes transients vaginal smooth muscle hypersensitivity and urethral sphincter dysfunction

BACKGROUND

Although pelvic floor dysfunction (PFD) has a multifactorial etiology, pregnancy and childbirth are considered crucial events predisposing to urinary incontinence as well as pelvic organ prolapse, which are highly prevalent. Rats are the most frequently used animal model and pudendal nerve crush (PNC) and vaginal distension (VD) are often used to mimic vaginal delivery.

OBJECTIVE

To document the time course of events after simulated vaginal delivery (SVD) on the urethral sphincter and the vaginal smooth muscle layer.

MATERIALS AND METHODS

Virgin female Sprague-Dawley rats were subjected to SVD (PNC + VD) or sham surgery and evaluated at 7, 14, 21, and 42 days after the injury. Urethral function was determined in vivo by microultrasound during cystometry and vaginal smooth muscle layer was harvested for in vitro pharmacologic investigation by isometric tension recording. Furthermore, vaginal and urethral samples were investigated by immunohistochemistry and real-time quantitative polymerase chain reaction.

RESULTS

Microultrasound showed no bursting of the urethral sphincter in the SVD group at 7 days with a functional recovery starting at 14 days, and normal bursting at 21 and 42 days. Vaginal smooth muscle showed higher sensitivity to carbachol at 14 and 21 days after injury; however, at 42 days, its sensitivity decreased when compared with sham.

CONCLUSION

SVD induces urethral dysfunction and a shift in vaginal smooth muscle contractile responses to carbachol.

Pharmacological modulation of the spatiotemporal disposition of micromotions in the intact resting urinary bladder of the rabbit; their pattern is under both myogenic and autonomic control

OBJECTIVES

To explore and characterize the disposition and dynamics of micromotions in the wall of the intact resting teradotoxinized urinary bladder of the rabbit before and after the administration of adrenergic and cholinergic pharmaceutical agents.

METHODS

Spatiotemporal maps and related intravesical pressure were used to analyse propagating patches of contractions (PPCs) and their component individual myogenic contractions [propagating individual contractions (PICs)] in the wall of the tetradotoxinized urinary bladder.

RESULTS

The bladder wall exhibited two contractile states that were of similar frequencies to those of the two types of electrophysiological discharge described in previous studies; the first, in which cyclic PPCs predominated, the second in which small irregular PICs predominated. The addition of carbachol increased the size, frequency, speed and distance of propagation of PPCs, whereas the addition of isoprenaline temporarily halted the incorporation of PICs into PPCs, and reduced patch size and total area undergoing contraction. The RhoA kinase (ROCK) inhibitor Y-27632 reduced both largest patch index and mean patch size. Both carbenoxolone and ROCK inhibition decreased the duration of PPCs. Carbenoxolone also prolonged duration and accelerated PPC propagation velocity. The authors postulate that these differences arise from differing effects of these agents on myocytes and interstitial cells within the stress environment of the bladder, influencing the development, coordination and propagation of PPCs.

CONCLUSIONS

The timings and structure of spontaneous micromotions in the wall of the isolated bladder change when it is treated with sympathetic/parasympathetic agonists and with myogenically active agents. Correspondingly, disorders of bladder wall contraction may result from disorders of either neurogenic or myogenic signalling and may be amenable to treatment with combinations of agents that influence both.

[S2e guideline of the German urologists: Conservative and pharmacologic treatment of benign prostatic hyperplasia]

This report summarizes the relevant aspects of the S2e guideline of the German Urologists for the conservative and pharmacological treatment of lower urinary tract symptoms due to benign prostatic hyperplasia. Recommendations are given regarding watchful waiting, behavioral therapy, phytotherapy and pharmacological mono- and combination therapy. The influence of the different therapeutic options on bladder outlet obstruction (BOO) is described in detail.

Regulation of urinary bladder function by protein kinase C in physiology and pathophysiology

BACKGROUND

Protein kinase C (PKC) is expressed in many tissues and organs including the urinary bladder, however, its role in bladder physiology and pathophysiology is still evolving. The aim of this review was to evaluate available evidence on the involvement of PKC in regulation of detrusor contractility, muscle tone of the bladder wall, spontaneous contractile activity and bladder function under physiological and pathophysiological conditions.

METHODS

This is a non-systematic review of the published literature which summarizes the available animal and human data on the role of PKC signaling in the urinary bladder under different physiological and pathophysiological conditions. A wide PubMed search was performed including the combination of the following keywords: "urinary bladder", "PKC", "detrusor contractility", "bladder smooth muscle", "detrusor relaxation", "peak force", "detrusor underactivity", "partial bladder outlet obstruction", "voltage-gated channels", "bladder nerves", "PKC inhibitors", "PKC activators". Retrieved articles were individually screened for the relevance to the topic of this review with 91 citations being selected and included in the data analysis.

DISCUSSION

Urinary bladder function includes the ability to store urine at low intravesical pressure followed by a subsequent release of bladder contents due to a rapid phasic contraction that is maintained long enough to ensure complete emptying. This review summarizes the current concepts regarding the potential contribution of PKC to contractility, physiological voiding, and related signaling mechanisms involved in the control of both the storage and emptying phases of the micturition cycle, and in dysfunctional voiding. Previous studies linked PKC activation exclusively with an increase in generation of the peak force of smooth muscle contraction, and maximum force generation in the lower urinary tract. More recent data suggests that PKC presents a broader range of effects on urinary bladder function including regulation of storage, emptying, excitability of the detrusor, and bladder innervation. In this review, we evaluated the mechanisms of peripheral and local regulation of PKC signaling in the urinary bladder, and their impact on different phases of the micturition cycle under physiological and pathophysiological conditions.

Anatomy and physiology of the lower urinary tract

Functions of the lower urinary tract to store and periodically eliminate urine are regulated by a complex neural control system in the brain, spinal cord, and peripheral autonomic ganglia that coordinates the activity of smooth and striated muscles of the bladder and urethral outlet. Neural control of micturition is organized as a hierarchic system in which spinal storage mechanisms are in turn regulated by circuitry in the rostral brainstem that initiates reflex voiding. Input from the forebrain triggers voluntary voiding by modulating the brainstem circuitry. Many neural circuits controlling the lower urinary tract exhibit switch-like patterns of activity that turn on and off in an all-or-none manner. The major component of the micturition switching circuit is a spinobulbospinal parasympathetic reflex pathway that has essential connections in the periaqueductal gray and pontine micturition center. A computer model of this circuit that mimics the switching functions of the bladder and urethra at the onset of micturition is described. Micturition occurs involuntarily during the early postnatal period, after which it is regulated voluntarily. Diseases or injuries of the nervous system in adults cause re-emergence of involuntary micturition, leading to urinary incontinence. The mechanisms underlying these pathologic changes are discussed.

Neuromuscular nicotinic receptors mediate bladder contractions following bladder reinnervation with somatic to autonomic nerve transfer after decentralization by spinal root transection

PURPOSE

We investigated whether the reinnervated neuronal pathway mediates contraction via the same neurotransmitter and receptor mechanisms as the original pathway.

MATERIALS AND METHODS

After decentralizing the bladder by transecting the sacral roots in dogs we performed peripheral nerve transfer, including bilateral genitofemoral to pelvic nerve transfer and unilateral left femoral nerve to bilateral pelvic nerve transfer. Reinnervation was assessed 7.5 months postoperatively by monitoring bladder pressure during electrical stimulation of the transferred nerves, spinal ventral roots and spinal cord.

RESULTS

Of the 17 dogs with genitofemoral to pelvic nerve transfer 14 (82%) demonstrated functional bladder reinnervation as evidenced by increased bladder pressure during stimulation of the transferred genitofemoral nerve, or L3 or L4 spinal ventral roots. Lumbar spinal cord stimulation caused increased bladder pressure in 9 of 10 dogs (90%) with unilateral left femoral nerve to bilateral pelvic nerve transfer. Succinylcholine virtually eliminated the bladder pressure increases induced by electrical stimulation of the transferred somatic nerves or of the lumbar spinal segments that contribute axons to these donor nerves. In unoperated or sham operated controls succinylcholine had no effect on nerve evoked bladder pressure increases but it substantially decreased the urethral and anal sphincter pressure induced by stimulating the lumbosacral spinal cord or the S2-S3 spinal ventral roots. The reinnervated detrusor muscles of dogs with genitofemoral to pelvic nerve transfer and unilateral left femoral nerve to bilateral pelvic nerve transfer also showed increased α1 nicotinic receptor subunit immunoreactivity in punctate dots on detrusor muscle fascicles and in neuronal cell bodies. This staining was not observed in controls.

CONCLUSIONS

Succinylcholine sensitive nicotinic receptors, which normally mediate only skeletal muscle neuromuscular junction neurotransmission, appeared in the new neuronal pathway after genitofemoral to pelvic and unilateral femoral nerve to bilateral pelvic nerve transfer. This suggests end organ neuroplasticity after reinnervation by somatic motor axons.

Impact of Rho-Kinase Inhibitor Hydroxyfasudil in Protamine Sulphate Induced Cystitis Rat Bladder

OBJECTIVES

The objective of the present study was to evaluate anti-inflammatory effects of hydroxyfasudil in a protamine sulfate (PS) induced cystitis rat model. Additionally, we investigated prevention of bladder overactivity (BO), and tissue damage in these experiments.

METHODS

Animals were divided into four groups. In Groups 1 and 2, chemical induced cystitis model was created by administrating intravesical PS with PE50 catheter by the transurethral route. In Group 1, Rho-kinase inhibitor hydroxyfasudil was administered intaperitoneally, and in Group 2, subjects were administered a corresponding volume of saline in the same way. In Group 3, vehicle was administered intravesically and hydroxyfasudil was administrated intraperitoneally. Group 4 was a control Group, and the vehicle was administered intravesically and intraperitoneally. Micturition frequencies were recorded. Biochemical analyses were performed for oxidative stress, and pathological evaluations were investigated. In vitro contractions of bladder tissue strips were measured in tissue-bath.

RESULTS

There were significantly lower Lipid peroxidase levels and higher levels of Glutathione in Group 1 than Group 2 (P = 0.016, P = 0.001, respectively). There was generally more inflammation in Group 2 than the other groups as determined by microscopy. There were significantly higher frequencies of micturition, lower volume, and mean voided maximum urine output after PS administration in Groups 1 and 2. In vitro contraction responses of bladder strips to potassium chloride and acetylcholine were statistically higher in Group 2 than Groups 1 and 3.

CONCLUSIONS

Significant reduction of inflammation by affecting the anti-oxidant defense systems was provided by hydroxyfasudil. Decreased in vitro responses to contractions of bladder smooth muscle strips were obtained. Hydroxyfasudil may be a potential new therapeutic option for inflammation and BO, in rat bladder.

Functional and molecular changes of the bladder in rats with crushing injury of nerve bundles from major pelvic ganglion to the bladder: role of RhoA/Rho kinase pathway

Voiding dysfunction is a common complication after radical pelvic surgery. To reduce this complication, nerve-sparing radical pelvic surgery was introduced. However, several patients experienced voiding difficulty despite nerve-sparing radical pelvic surgery. Thus, we investigated the functional and molecular changes of the bladder in rats, which demonstrated voiding dysfunction induced by nerve damage during nerve-sparing radical pelvic surgery. Male rats were used and assigned to normal, sham-operated, and bilateral crushing nerve bundles from major pelvic ganglion (MPG) to bladder group. After one, two, and four-week crushing injury, significantly decreased contractile response and increased connective tissue of the detrusor were observed and these results were reliable findings with voiding difficulty following nerve-sparing radical pelvic surgery. After crushing injury, significantly increased M2 muscarinic receptor expression was observed and this might be regarded as the compensatory response. However, M3 muscarinic receptor expression was not significantly changed. The expression of RhoA, ROCK-α, and ROCK-β was significantly increased after one, two, and four-week crushing injury. From these results, the down-regulation of RhoA/Rho kinase pathway might lead to the decreased bladder contractility after crushing injury of nerve bundles from MPG to the bladder despite of the compensated up-regulation of M2 muscarinic receptor.

Gastric body cholinergic contractile signal transduction in M2 and M3 receptor knockout mice

Although most smooth muscles express a greater density of M2 than M3 muscarinic receptors, based on the potency of subtype selective muscarinic receptor antagonists, the M3 subtype predominantly mediates contraction. The effect of inhibitors of putative contractile signal transduction pathway enzymes on carbachol-induced contractions was determined in wild-type (WT) mice and mice lacking either the M2 (M2KO) or the M3 (M3KO) receptor subtype. Contractile responses to KCl, then increasing carbachol concentrations in the presence and absence of enzyme inhibitors was determined. The KCl-induced contraction was not different between strains. The carbachol response was unaffected in the M2KO strain but decreased 42% in M3KO mice (p < 0.01). Darifenacin potency was high in both WT and M2KO strains, indicating M3-mediated contractions, and low in the M3KO strain, suggesting M2-mediated contractions. The phosphatidyl inositol-specific phospholipase C (Pi-PLC) inhibitor ET-18-OCH3 had no effect. Inhibition of phosphatidyl choline-specific phospholipase C (PC-PLC) and sphingomyelin synthase with D609 decreased maximal contraction in all strains. M3-mediated contractions in the M2KO strain were decreased 54% by the protein kinase C (PKC) inhibitor chelerythrine. M2-mediated contractions in the M3KO and WT strains were decreased by the Rho kinase (ROCK) inhibitor Y27632 as well as the ROCK, PKA and PKG inhibitor H89. The M3 subtype activates PKC and either PC-PLC or sphingomyelin synthase, while the M2 subtype activates ROCK and either PC-PLC or sphingomyelin synthase. These studies suggest that multiple parallel pathways mediate cholinergic contractions in stomach body smooth muscle.

Anatomical feasibility of performing a nerve transfer from the femoral branch to bilateral pelvic nerves in a cadaver: a potential method to restore bladder function following proximal spinal cord injury

OBJECT

Nerve transfers are an effective means of restoring control to paralyzed somatic muscle groups and have recently been shown to be effective in denervated detrusor muscle in a canine model. A cadaveric study was performed to examine the anatomical feasibility of transferring femoral muscular nerve branches to vesical branches of the pelvic nerve as a method of potentially restoring innervation to control the detrusor muscle in humans.

METHODS

Twenty cadavers were dissected bilaterally to expose pelvic and femoral muscular nerve branches. Ease of access and ability to transfer the nerves were assessed, as were nerve cross-sectional areas.

RESULTS

The pelvic nerve was accessed at the base of the bladder, inferior to the ureter, and accompanied by inferior vesical vessels. Muscular branches of the femoral nerve to the vastus medialis and intermedius muscles (L-3 and L-4 origins) were followed distally for 17.4 ± 0.8 cm. Two muscle branches were split from the femoral nerve trunk, and tunneled inferior to the inguinal ligament. One branch was moved medially toward the base of the bladder and linked to the ipsilateral pelvic nerve. The second branch was tunneled superior to the bladder and linked to the contralateral pelvic nerve. The cross-sectional area of the pelvic nerve vesical branch was 2.60 ± 0.169 mm(2) (mean ± SEM), and the femoral nerve branch at the suggested transection site was 4.40 ± 0.41 mm2.

CONCLUSIONS

Use of femoral nerve muscular branches from the vastus medialis and intermedius muscles for heterotopic nerve transfer of bilateral pelvic nerves is surgically feasible, based on anatomical location and cross-sectional areas.

Muscarinic agonists and antagonists: effects on the urinary bladder

Voiding of the bladder is the result of a parasympathetic muscarinic receptor activation of the detrusor smooth muscle. However, the maintenance of continence and a normal bladder micturition cycle involves a complex interaction of cholinergic, adrenergic, nitrergic and peptidergic systems that is currently little understood. The cholinergic component of bladder control involves two systems, acetylcholine (ACh) released from parasympathetic nerves and ACh from non-neuronal cells within the urothelium. The actions of ACh on the bladder depend on the presence of muscarinic receptors that are located on the detrusor smooth muscle, where they cause direct (M₃) and indirect (M₂) contraction; pre-junctional nerve terminals where they increase (M₁) or decrease (M₄) the release of ACh and noradrenaline (NA); sensory nerves where they influence afferent nerve activity; umbrella cells in the urothelium where they stimulate the release of ATP and NO; suburothelial interstitial cells with unknown function; and finally, other unidentified sites in the urothelium from where prostaglandins and inhibitory/relaxatory factors are released. Thus, the actions of muscarinic receptor agonists and antagonists on the bladder may be very complex even when considering only local muscarinic actions. Clinically, muscarinic antagonists remain the mainstay of treatment for the overactive bladder (OAB), while muscarinic agonists have been used to treat hypoactive bladder. The antagonists are effective in treating OAB, but their precise mechanisms and sites of action (detrusor, urothelium, and nerves) have yet to be established. Potentially more selective agents may be developed when the cholinergic systems within the bladder are more fully understood.

Effect of pre-contraction on β-adrenoceptor-mediated relaxation of rat urinary bladder

PURPOSE

The human physiological bladder contraction is largely mediated by acetylcholine acting on muscarinic receptors, but in pathophysiological settings the relative role of non-cholinergic stimuli gains importance. β-Adrenoceptor agonists are currently in clinical development as treatments for the overactive bladder syndrome. Therefore, we have explored the ability of the β-adrenoceptor agonist isoprenaline to induce rat isolated bladder strip relaxation on pre-contraction with the muscarinic agonist carbachol as compared to bladder tone induced by several non-cholinergic stimuli.

METHODS

Bladder tone was induced by passive tension, receptor independently by KCl, carbachol, bradykinin or serotonin. Concentration–response curves were generated for relaxation by isoprenaline, and a single concentration of the receptor-independent relaxant forskolin was also tested.

RESULTS

The various contractile stimuli induced different degrees of bladder tone, but the ability of isoprenaline or forskolin to relax rat bladder was not correlated with the degree of tone. Isoprenaline was significantly less potent and effective in causing relaxation against carbachol-induced tone than against any other stimulus, whereas no such relationship was observed for forskolin.

CONCLUSIONS

We conclude that β-adrenoceptor agonists can induce rat bladder relaxation against a wide range of contractile stimuli and are more potent and/or effective against non-cholinergic stimuli than against muscarinic agonism. This profile appears desirable for agents intended for the treatment of overactive bladder.

Effects of fasudil, a Rho-kinase inhibitor, on contraction of pig bladder tissues with or without urothelium

OBJECTIVES

To investigate the effects of fasudil, a Rho-associated serine-threonine protein kinase inhibitor, on contraction of the pig urinary bladder tissues with or without urothelium.

METHODS

Cumulative concentration-response curves (CRCs) to carbachol were obtained with and without 3-10 microM fasudil. Drug effects were evaluated in detrusor with and without urothelium. Inhibitory responses to fasudil were also examined in tissues precontracted with KCl and carbachol, and in response to electrical field stimulation, in pig bladder with and without urothelium.

RESULTS

In detrusor without urothelium, maximum contraction (E(max)) decreased after administration of fasudil at 3 or 10 micromol/L (both P < 0.01), or 30 micromol/L (72.5 + or - 7.43%, 58.4 + or - 8.04% and 68.4 + or - 9.6%, respectively, of the first curve). In detrusor with urothelium, E(max) decreased significantly (all P < 0.05) after the addition of 3, 10 or 30 micromol/L of fasudil (84.9 + or - 6.7%, 67.9 + or - 5.2% and 35.2 + or - 4.1%, respectively). In tissues precontracted with 80 mmol/L KCl or 100 micromol/L carbachol, tension after administration of fasudil (1 nmol/L to 100 micromol/L) decreased (by approximately 40%), only after administration of fasudil at high concentration (>1 micromol/L), in detrusor both with and without urothelium. In tissues with and without urothelium, responses to electrical field stimulation at 1-50 Hz decreased significantly in a concentration-dependent manner after addition of fasudil (3 to 30 micromol/L).

CONCLUSIONS

Fasudil seems to provoke relaxation of the bladder detrusor via both urothelium-dependent and independent pathways.

A refocus on the bladder as the originator of storage lower urinary tract symptoms: a systematic review of the latest literature

CONTEXT

The focus of clinical understanding and management of male storage lower urinary tract symptoms (LUTS) has shifted from the prostate to the bladder. This is mirrored by an increasing body of experimental evidence suggesting that the bladder is the central organ in the pathogenesis of LUTS.

OBJECTIVE

A systematic review of the literature available on pathophysiologic aspects of storage LUTS.

EVIDENCE ACQUISITION

Medline was searched for the period ending December 2008 for studies on human and animal tissue exploring possible functional and structural alterations underlying bladder dysfunction. Further studies were chosen on the basis of manual searches of reference lists and review papers.

EVIDENCE SYNTHESIS

Numerous recent publications on LUTS pathophysiology were identified. They were grouped into studies exploring abnormalities on urothelial/suburothelial, muscular, or central levels.

CONCLUSIONS

Studies revealed both structural and functional alterations in bladders from patients with LUTS symptoms or animals with experimentally induced bladder dysfunction. In particular, the urothelium and the suburothelial space, containing afferent nerve fibres and interstitial cells, have been found to form a functional unit that is essential in the process of bladder function. Various imbalances within this suburothelial complex have been identified as significant contributors to the generation of storage LUTS, along with potential abnormalities of central function.

Mechanisms of adaptive supersensitivity in vas deferens

Adaptive supersensitivity is a phenomenon characteristic of excitable tissues and discloses as a compensatory adjustment of tissue's response to unrelated stimulatory endogenous and exogenous substances after chronic interruption of excitatory neurotransmission. The mechanisms underlying such higher postjunctional sensitivity have been postulated for a variety of cell types. In smooth muscles, especially the vas deferens with its rich sympathetic innervation, the mechanisms responsible for supersensitivity are partly understood and appear to be different from one species to another. The present review provides a general understanding of adaptive supersensitivity and emphasizes early and recent information about the putative mechanisms involved in this phenomenon in rodent vas deferens.

Similarities and differences in the autonomic control of airway and urinary bladder smooth muscle

The airways and the urinary bladder are both hollow organs serving very different functions, i.e. air flow and urine storage, respectively. While the autonomic nervous system seems to play only a minor if any role in the physiological regulation of airway tone during normal breathing, it is important in the physiological regulation of bladder smooth muscle contraction and relaxation. While both tissues share a greater expression of M2 than of M3 muscarinic receptors, smooth muscle contraction in both is largely mediated by the smaller M3 population apparently involving phospholipase C activation to only a minor if any extent. While smooth muscle in both tissues can be relaxed by beta-adrenoceptor stimulation, this primarily involves beta2-adrenoceptors in human airways and beta3-adrenoceptors in human bladder. Despite activation of adenylyl cyclase by either subtype, cyclic adenosine monophosphate plays only a minor role in bladder relaxation by beta-agonists; an important but not exclusive function is known in airway relaxation. While airway beta2-adrenoceptors are sensitive to agonist-induced desensitization, beta3-adrenoceptors are generally considered to exhibit much less if any sensitivity to desensitization. Gene polymorphisms exist in the genes of both beta2- and beta3-adrenoceptors. Despite being not fully conclusive, the available data suggest some role of beta2-adrenoceptor polymorphisms in airway function and its treatment by receptor agonists, whereas the available data on beta3-adrenoceptor polymorphisms and bladder function are too limited to allow robust interpretation. We conclude that the distinct functions of airways and urinary bladder are reflected in a differential regulation by the autonomic nervous system. Studying these differences may be informative for a better understanding of each tissue.

Rho-kinase and effects of Rho-kinase inhibition on the lower urinary tract

Altered smooth muscle cell contractility/tone contributes, at least in part, to the lower urinary tract symptoms (LUTS) seen in men with benign prostatic obstruction (BPO). Accordingly, many of the therapies to date have focused largely on blockade of individual membrane receptors to diminish smooth muscle contractility and provide symptomatic relief. This pharmacologic approach has been associated with variable results, limited efficacy, and untoward side effects. Such limited clinical success is not surprising given the plethora of neurotransmitters, neuromodulators, and hormones that are now known to modulate LUT smooth muscle cell tone. In the pursuit of improved treatment options, more recent investigations have focused attention on intracellular signal transduction events that represent convergence points for membrane receptor activation. In particular, calcium sensitization and the role of the Rho-kinase pathway has received much attention. In this report, we review the literature on the role of the Rho-kinase pathway in the modulation of LUT smooth muscle cell tone. In short, the available data support an important role for Rho-kinase in the physiologic and pathophysiologic regulation of LUT smooth muscle cell tone. Rho-kinase inhibitors thus appear to represent a potentially attractive therapeutic possibility for the treatment of LUTS.

Refinement in the management of the denervated canine urinary bladder using an abdominal vesicostomy

Treatment of the neurogenic bladder in canine models of spinal cord injury presents challenges in ensuring bladder drainage. While vesicostomy is routine for humans, the procedure is not common in canines. Our study of bladder reinnervation involved transection of the nerve roots that mediate bladder contraction in 34 canines. An abdominal vesicostomy was created by fixing the everted mucosa to the skin incision. After euthanasia, we assessed the contractility of in vitro bladder muscle strips in response to muscarinic receptor stimulation. There were a total of 11 complications in 9 of the 34 animals. In two animals, the vesicostomy narrowed such that it could not be catheterized and in two other animals the vesicostomy closed to between 5 and 10 mm diameter. Another animal removed the stitches prior to complete healing, requiring further surgical procedures. In fi ve animals, partial prolapse of the bladder through the vesicostomy required surgical repair, and in one animal the bladder became infected and required antibiotic treatment. In the few animals in which irritation resulted from the constant contact of urine with the skin, daily topical application of petrolatum ointment alleviated this symptom. Gross inspection of the bladder at euthanasia and in vitro contractility of bladder muscle strips from these animals revealed no evidence of changes associated with bladder hypertrophy. This study demonstrated that permanent cutaneous vesicostomy is an optimal refinement method for management of the neurogenic bladder in canines. The procedure avoids the distress as well as potential bladder hypertrophy induced by multiple daily interventions to empty the bladder by either catheterization or manual compression.

Signal transduction underlying the control of urinary bladder smooth muscle tone by muscarinic receptors and beta-adrenoceptors

The normal physiological contraction of the urinary bladder, which is required for voiding, is predominantly mediated by muscarinic receptors, primarily the M₃ subtype, with the M₂ subtype providing a secondary backup role. Bladder relaxation, which is required for urine storage, is mediated by β-adrenoceptors, in most species involving a strong β₃-component. An excessive stimulation of contraction or a reduced relaxation of the detrusor smooth muscle during the storage phase of the micturition cycle may contribute to bladder dysfunction known as the overactive bladder. Therefore, interference with the signal transduction of these receptors may be a viable approach to develop drugs for the treatment of overactive bladder. The prototypical signaling pathway of M₃ receptors is activation of phospholipase C (PLC), and this pathway is also activated in the bladder. Nevertheless, PLC apparently contributes only in a very minor way to bladder contraction. Rather, muscarinic-receptor-mediated bladder contraction involves voltage-operated Ca²⁺ channels and Rho kinase. The prototypical signaling pathway of β-adrenoceptors is an activation of adenylyl cyclase with the subsequent formation of cAMP. Nevertheless, cAMP apparently contributes in a minor way only to β-adrenoceptor-mediated bladder relaxation. BK_Ca channels may play a greater role in β-adrenoceptor-mediated bladder relaxation. We conclude that apart from muscarinic receptor antagonists and β-adrenoceptor agonists, inhibitors of Rho kinase and activators of BK_Ca channels may have potential to treat an overactive bladder.

Does phospholipase C mediate muscarinic receptor-induced rat urinary bladder contraction?

Muscarinic acetylcholine receptors, particularly M(3) receptors, are physiologically the most important mechanism to induced urinary bladder smooth muscle contraction. Their prototypical signaling response is a stimulation of phospholipase C (PLC), and this also has been shown in the urinary bladder. Nevertheless, it has remained controversial whether PLC signaling mediates bladder contraction induced by muscarinic receptor agonists. Studies in favor and against a role for PLC differed in their experimental protocol (single versus repeated concentration-response curves within a single preparation) and in the PLC inhibitors that have been used. We have now tested whether previous differential conclusions regarding a role for PLC are related to inhibitors and/or experimental protocols. In a single curve protocol, U-73,122 [1-[6-[((17beta)-3-methoxyestra-1,3,5[10]-trien-17-yl)amino]hexyl]-1H-pyrrole-2,5-dione] did not attenuate carbachol responses. In a repeated curve protocol, ET-18-OCH(3) (1-O-octadecyl-2-O-methyl-sn-glycero-3-phosphorylcholine) lacked significant inhibition relative to vehicle time controls. In contrast, D609 (O-tricyclo[5.2.1.02,6]dec-9-yl dithiocarbonate potassium salt) depressed maximal carbachol effects but also nonspecifically inhibited contraction induced by KCl. Neomycin did not affect the carbachol-induced rat urinary bladder contraction. We conclude that previously reported differences relate to the use of inhibitors rather than experimental protocols and that the overall data do not support a role for PLC in M(3) muscarinic receptor-mediated rat bladder contraction.

LUTS treatment: Future treatment options

Lower urinary tract symptoms (LUTS) are commonly divided into storage, voiding, and postmicturition symptoms, and may occur in both men and women. Male LUTS have historically been linked to benign prostatic hyperplasia (BPH), but are not necessarily prostate related. The focus of treatment for LUTS has thus shifted from the prostate to the bladder and other extraprostatic sites. LUTS include symptoms of the overactive bladder (OAB), which are often associated with detrusor overactivity. Treatment for LUTS suggestive of BPH has traditionally involved the use of alpha(1)-adrenoceptor (AR) antagonists; 5alpha-reductase inhibitors; and phytotherapy-however, several new therapeutic principles have shown promise. Selective beta(3)-adrenoceptor agonists and antimuscarinics are potentially useful agents for treating LUTS, particularly for storage symptoms secondary to outflow obstruction. Other agents of potential or actual importance are antagonists of P2X(3) receptors, botulinum toxin type A, endothelin (ET)-converting enzyme inhibitors, and drugs acting at vanilloid, angiotensin, and vitamin D(3) receptor sites. Drugs interfering with the nitric oxide/cGMP-cAMP pathway, Rho-kinase and COX inhibitors, as well as drugs targeting receptors and mechanisms within the CNS, are also of interest and deserving of further study for the treatment of LUTS.

Rho kinase: a target for treating urinary bladder dysfunction?

Urinary incontinence and other urinary storage symptoms are frequent in the general population but available treatments have limited efficacy and tolerability. Rho kinase (ROCK) has a central role in the regulation of smooth muscle contraction, including that of the urinary bladder. Recent experimental evidence indicates that this role could be deregulated and exacerbated in local and systemic pathological conditions that affect the bladder. In vitro studies with prototypical ROCK inhibitors such as Y27632 and in vivo data from animal models indicate that such drugs have potential as future treatments for bladder dysfunction.