Localization of nitric oxide synthase activity in the human lower urinary tract and its correlation with neuroeffector responses

Expression of Phosphodiesterase (PDE) Isoenzymes in the Human Male and Female Urethra

Purpose

Although it has been supposed that the NO/cyclic GMP system produces inhibitory signals to reduce the resistance of the bladder outlet and urethra during the micturition phase, little is known on the mechanisms controlling the function of urethral smooth muscle. The aim of the present study was to examine in the male and female urethra the expression of phosphodiesterase (PDE) isoenzymes, known as key proteins of the cyclic GMP/AMP signaling.

Methods

Urethral tissue was obtained from 4 female cadavers and 7 male patients (who had undergone gender reassignment surgery). The expression of mRNA encoding for PDE1A, 1B, 1C, 2A, 4B, 4D, 5A, 10A and 11A was investigated by means of real-time polymerase chain reaction. Western blot (WB) analysis was conducted to detect PDE isoenzymes.

Results

RT-PCR revealed relevant amounts of mRNA encoding for PDE1A, 2A, 4B, 5A, 10A and 11A in male and female urethral tissue. The expression of PDE1A, 2A, 4B and 10A was 2-fold higher in the female than in the male urethra, whereas the expression of PDE11A mRNA was 7-fold higher in the male tissue. In the WB experiments, immunosignals specific for PDE1A, PDE4A and 4B and PDE11A were of higher degree in the female than the male tissue specimens, while an almost equivocal expression of PDE2A, PDE5A and PDE10A was registered.

Conclusion

On the level of mRNA and function proteins, different patterns of expression of PDE isoenzymes were registered in human male and female urethra. Future studies may clarify whether inhibition of PDE isoenzymes is likely to facilitate the relaxation of the outflow region in both sexes.

Evaluation of a rat model of functional urinary bladder outlet obstruction produced by chronic inhibition of nitric oxide synthase

AIMS

Ligation of the urethra to create partial bladder outlet obstruction has widely been used as an animal model of bladder obstruction, although obstructive bladder dysfunction may be due to both mechanical and functional obstruction. Previous studies in rodents have demonstrated that long-term nitric oxide (NO) deficiency can lead to detrusor overactivity, and lack of NO may thus cause impairment of bladder outlet relaxation. The aim of this study was to define the characteristics of bladder and urethral dysfunction induced by chronic NO deficiency through both in vivo and in vitro investigations.

MAIN METHODS

Rats were divided into two groups, and one group received an NO synthase inhibitor (N_ω-nitro-L-arginine methyl ester hydrochloride: L-NAME) in the drinking water for 4 weeks. Bladder and urethral function were evaluated by continuous cystometry and isovolumetric cystometry. In vitro functional studies of detrusor strips and measurement of the mRNA and protein expression of an ischemic marker and a gap junction protein were also performed in separate rats.

KEY FINDINGS

L-NAME administration raised blood pressure and decreased plasma nitrite/nitrate level compared to the control group. L-NAME treatment increased the frequency of bladder contractions and the residual volume, and elevated urethral pressure and bladder contraction pressure. In addition, carbachol-induced contraction was reduced in isolated detrusor strips from the L-NAME group, and bladder expression of HIF-1 and connexin 43 showed upregulation.

SIGNIFICANCE

These findings suggest that chronic administration of L-NAME to rats induces bladder hyperactivity with residual urine, and may provide a useful model of functional bladder obstruction.

Inhibition of vascular smooth muscle inward-rectifier K+ channels restores myogenic tone in mouse urinary bladder arterioles

Prolonged decreases in urinary bladder blood flow are linked to overactive and underactive bladder pathologies. However, the mechanisms regulating bladder vascular reactivity are largely unknown. To investigate these mechanisms, we examined myogenic and vasoactive properties of mouse bladder feed arterioles (BFAs). Unlike similar-sized arterioles from other vascular beds, BFAs failed to constrict in response to increases in intraluminal pressure (5-80 mmHg). Consistent with this lack of myogenic tone, arteriolar smooth muscle cell membrane potential was hyperpolarized (-72.8 ± 1.4 mV) at 20 mmHg and unaffected by increasing pressure to 80 mmHg (-74.3 ± 2.2 mV). In contrast, BFAs constricted to the thromboxane analog U-46619 (100 nM), the adrenergic agonist phenylephrine (10 µM), and KCl (60 mM). Inhibition of nitric oxide synthase or intermediate- and small-conductance Ca²⁺-activated K⁺ channels did not alter arteriolar diameter, indicating that the dilated state of BFAs is not attributable to overactive endothelium-dependent dilatory influences. Myocytes isolated from BFAs exhibited BaCl₂ (100 µM)-sensitive K⁺ currents consistent with strong inward-rectifier K⁺ (K_IR) channels. Notably, block of these K_IR channels "restored" pressure-induced constriction and membrane depolarization. This suggests that these channels, in part, account for hyperpolarization and associated absence of tone in BFAs. Furthermore, smooth muscle-specific knockout of K_IR2.1 caused significant myogenic tone to develop at physiological pressures. This suggests that 1) the regulation of vascular tone in the bladder is independent of pressure, insofar as pressure-induced depolarizing conductances cannot overcome K_IR2.1-mediated hyperpolarization; and 2) maintenance of bladder blood flow during bladder filling is likely controlled by neurohumoral influences.

Latest Evidence on the Use of Phosphodiesterase Type 5 Inhibitors for the Treatment of Lower Urinary Tract Symptoms Secondary to Benign Prostatic Hyperplasia

CONTEXT

Several preclinical reports, randomized controlled trials, systematic reviews, and posthoc analyses corroborate the role of phosphodiesterase type 5 inhibitors (PDE5-Is) in the treatment of men with lower urinary tract symptoms (LUTS) associated with benign prostatic enlargement (BPE).

OBJECTIVE

Update of the latest evidence on the mechanisms of action, evaluate the current meta-analyses, and emphasize the results of pooled data analyses of PDE5-Is in LUTS/BPE.

EVIDENCE ACQUISITION

Literature analysis of basic researches on PDE5-Is, systematic literature search in PubMed and Scopus until May 2015 on reviews of trials on PDE5-Is, and collection of pooled data available on tadalafil 5mg.

EVIDENCE SYNTHESIS

Latest evidences on the pathophysiology of LUTS/BPE has provided the rationale for use of PDE5-Is: (1) improvement of LUT oxygenation, (2) smooth muscle relaxation, (3) negative regulation of proliferation and transdifferentiation of LUT stroma, (4) reduction of bladder afferent nerve activity, and (5) down-regulation of prostate inflammation are the proven mechanisms of action of PDE5-Is. Data from eight systematic reviews demonstrated that PDE5-Is allow to improve LUTS (International Prostate Symptom Score mean difference vs placebo: 2.35-4.21) and erectile function (International Index of Erectile Function mean difference vs placebo: 2.25-5.66), with negligible change in flow rate (Qmax mean difference vs placebo: 0.01-1.43). Pooled data analyses revealed that tadalafil 5mg once daily allows the clinically-meaningful improvement of LUTS and nocturnal voiding frequency independent of both erectile dysfunction severity and improvement.

CONCLUSIONS

PDE5-Is are safe and effective in improving both LUTS and erectile function in appropriately selected men with LUTS/BPE. Data on the reduction of disease progression, long-term outcomes, and cost-effectiveness analyses are still lacking.

PATIENT SUMMARY

We reviewed recent literature on phosphodiesterase type 5 inhibitors in men with lower urinary tract symptoms associated with prostatic enlargement. We found evidence to confirm that phosphodiesterase type 5 inhibitors are a valid treatment option for men affected by bothersome urinary symptoms with or without erectile dysfunction.

Lower urinary tract symptoms, benign prostatic hyperplasia and metabolic syndrome

Epidemiological studies have shown that age is the principal unmodifiable risk factor of lower urinary tract symptoms (LUTS). Until the past decade, the process of lower urinary tract ageing was, therefore, considered unmodifiable - as ageing per se. However, the traditional dogma that BPH-related LUTS (BPH-LUTS) is an immutable consequence of old age is no longer acceptable. Results from multiple preclinical and clinical studies indicate that several modifiable, age-related metabolic aberrations (metabolic syndrome, obesity, dyslipidaemia, diabetes) are important determinants in both the development and the progression of BPH-LUTS. Metabolic syndrome and its related comorbidities, such as sex steroid alterations and low-grade inflammation, have been related to BPH-LUTS development and progression. With the correct treatment and recommended lifestyle changes, many individuals with metabolic syndrome might be able to prevent or delay the onset of metabolic-syndrome-related complications; however, whether promoting healthier lifestyles can really alter a man's propensity to develop BPH-LUTS remains to be clarified.

Metabolic syndrome does not impair the response to alfuzosin treatment in men with lower urinary tract symptoms: a double-blind, randomized, placebo-controlled study

OBJECTIVE

This study is a placebo-controlled comparison of the response to alfuzosin treatment for lower urinary tract symptoms (LUTS) in patients with and without metabolic syndrome (MetS).

MATERIAL AND METHODS

A total of 80 men with LUTS were included in the study. Patients had a maximum flow rate of <15 mL/sec, prostate volume of >20 mL, and International Prostate Symptom Score (IPSS) of >8. All eligible men (n=68) for evaluation were initially divided into two groups as MetS (n=34) and non-MetS (n=34) groups. Patients were further randomized to receive alfuzosin (10 mg/day) or placebo (n=17/group; a total of four groups). The outcome was measured at 12(th) week according to the changes from baseline in IPSS, quality of life (QoL) scores, maximum flow rate (Qmax), and postmictional residue.

RESULTS

Alfuzosin significantly improved LUTS in men with and without MetS compared with patients receiving placebo (p<0.05). Mean IPSS scores in treatment groups decreased significantly, whereas patients receiving placebo had no statistically significant difference (p>0.05). Similarly, alfuzosin treatment resulted in a significant increase in Qmax in patients with LUTS/benign prostatic enlargement when compared with patients in placebo group (p<0.05). Mean QoL scores measured by IPSS-QoL and QoL questionnaires also improved significantly in patients receiving alfuzosin for 3 months regardless of the presence of MetS (p<0.05).

CONCLUSION

Our results revealed that the presence of MetS in patients with LUTS did not impair the response to alfuzosin treatment.

Effects of PDE5 Inhibitors and sGC Stimulators in a Rat Model of Artificial Ureteral Calculosis

Urinary colics from calculosis are frequent and intense forms of pain whose current pharmacological treatment remains unsatisfactory. New and more effective drugs are needed to control symptoms and improve stone expulsion. Recent evidence suggested that the Nitric Oxide (NO) / cyclic guanosine monophosphate (cGMP) / phosphodiesterase type 5 (PDE5) system may contribute to ureteral motility influencing stone expulsion. We investigated if PDE5 inhibitors and sGC stimulators influence ureteral contractility, pain behaviour and stone expulsion in a rat model of ureteral calculosis. We investigated: a)the sex-specific PDE5 distribution in the rat ureter; b)the functional in vitro effects of vardenafil and sildenafil (PDE5 inhibitors) and BAY41-2272 (sGC stimulator) on induced ureteral contractility in rats and c)the in vivo effectiveness of vardenafil and BAY41-2272, alone and combined with ketoprofen, vs hyoscine-N-butylbromide alone or combined with ketoprofen, on behavioural pain indicators and stone expulsion in rats with artificial calculosis in one ureter. PDE5 was abundantly expressed in male and female rats’ ureter. In vitro, both vardenafil and BAY41-2272 significantly relaxed pre-contracted ureteral strips. In vivo, all compounds significantly reduced number and global duration of “ureteral crises” and post-stone lumbar muscle hyperalgesia in calculosis rats. The highest level of reduction of the pain behaviour was observed with BAY41-2272 among all spasmolytics administered alone, and with the combination of ketoprofen with BAY41-2272. The percentage of stone expulsion was maximal in the ketoprofen+BAY41-2272 group. The NO/cGMP/PDE5 pathway is involved in the regulation of ureteral contractility and pain behaviour in urinary calculosis. PDE5 inhibitors and sGC stimulators could become a potent new option for treatment of urinary colic pain.

Lower urinary tract symptoms are associated with low levels of serum serotonin, high levels of adiponectin and fasting glucose, and benign prostatic enlargement

OBJECTIVE

The aim of this study was to test whether lower urinary tract symptoms (LUTS) and urinary incontinence are associated with the metabolic syndrome (MetS). The association between LUTS and benign prostatic enlargement (BPE) was also investigated.

MATERIAL AND METHODS

A cross-sectional, representative risk factor analysis of LUTS, as measured by the International Prostate Symptom Score (IPSS), and urinary incontinence was conducted. Among 950 representative individuals, aged 69-81 years, the association between clinical, anthropometric, endocrine, metabolic and inflammatory factors on the one hand, as both major and minor aspects of MetS, and LUTS and urinary incontinence, on the other hand, was analysed. The prostate gland volume was measured in a subgroup of 155 randomly selected individuals and the association between LUTS and BPE was estimated.

RESULTS

No significant association was found between LUTS or urinary incontinence and the major aspects of the MetS. However, in a multivariate analysis, serum serotonin showed an independent negative correlation with LUTS and with urinary incontinence while fasting serum glucose and serum adiponectin showed a positive correlation with LUTS. Furthermore, in a subgroup of 155 individuals, the prostate gland volume correlated positively with LUTS.

CONCLUSIONS

The study did not show an association between LUTS or urinary incontinence and the major components of the MetS. However, serum serotonin showed an independent negative correlation with LUTS and with urinary incontinence while fasting serum glucose and serum adiponectin showed a positive correlation with LUTS. The data confirm the general knowledge that BPE may be one of the causative factors of LUTS.

Pharmacologic characterization of human male urethral smooth muscle: an in vitro approach

OBJECTIVE

To elucidate the functional responses of isolated human urethral smooth muscle to various agents known to exert smooth muscle contraction or relaxation.

METHODS

Specimens of penile urethra were obtained from male patients who had undergone male-to-female gender reassignment surgery. Using the tissue bath technique, the contraction induced by increasing concentrations (1 nM-10 μM) of norepinephrine, phenylephrine, acetylcholine, carbachol, prostaglandin F2α, endothelin 1, angiotensin II, and oxytocin was measured. In another set-up, the effects of C-type natriuretic peptide (0.1 nM-1 μM), sodium nitroprusside, sildenafil, forskolin, alpha2-antagonist delquamine, and acetylcholine (1 nM/10 nM-10 μM) on the tension induced by norepinephrine were investigated. The production of cyclic guanosine monophosphate (GMP) and cyclic adenosine monophosphate (AMP) was measured by means of specific radioimmunoassays.

RESULTS

Endothelin 1, oxytocin, prostaglandin F2α, norepinephrine, and phenylephrine induced dose-dependent contraction of the isolated urethral tissue, whereas acetylcholine, carbachol, and angiotensin II had no or only minor contractile effects. The contraction induced by norepinephrine was reversed by the drugs with the following rank order of efficacy: sodium nitroprusside > delquamine > sildenafil > C-type natriuretic peptide > forskolin > acetylcholine. The maximal reversion of tension ranged from 68% (sodium nitroprusside) to 22% (acetylcholine). The relaxing effects of the drugs were paralleled by a several-fold increase in tissue levels of cyclic GMP and cyclic adenosine monophosphate.

CONCLUSION

The results provide evidence that urethral smooth muscle is under the control of endogenous compounds, such as adrenergic agonists (norepinephrine and phenylephrine), vasoactive peptides, prostagladins, NO/cyclic GMP, and acetylcholine, assumed to influence micturition at the peripheral level.

The impact of metabolic syndrome on the responsiveness to α1-blocker in men with BPH/LUTS

AIMS

Increasing evidence has proposed the components of metabolic syndrome (MtS) as risk factors for the development of benign prostate hyperplasia (BPH); therefore, it is thought that MtS may play a role in lower urinary tract symptoms related to BPH (BPH/LUTS) aetiology. Considering the closed relationships between MtS and BPH/LUTS, it is possible that patients with MtS might have different drug responsiveness in men with BPH/LUTS. We prospectively investigated the impact of MtS on responsiveness to α1-blocker in men with BPH/LUTS.

METHODS

We enrolled a total of 109 patients with a mean (SD) age of 59.8 (9.0) years, having a prostate volume of 20 cm(3) or greater with moderate to severe LUTS. All patients received doxazosin GITS (gastrointestinal therapeutic system) 4 mg once daily for a 12-week period of treatment. The efficacy measurement was assessed by the changes from baseline in the total IPSS, maximum urinary flow rate and postvoid residual urine volume. The drug responders were defined as those who had a total IPSS decrease of more than 4 points from baseline after 12 weeks of treatment.

RESULTS

Using multiple logistic regression analysis, our results showed that MtS was an independent factor for drug non-responder (OR = 4.26, p = 0.002). The rate of drug responder and total IPSS improvements in patients with MtS significantly decreased as the number of MtS components increased (p = 0.012 and p = 0.026). Among the MtS components, abnormal fasting blood glucose (FBG) was the most significantly independent factor for drug non-responder (OR = 3.17, p = 0.020).

CONCLUSION

This study suggested that the presence of MtS had a significantly negative impact on the responsiveness to α1-blocker in men with BPH/LUTS. Our results are important for BPH/LUTS patients who did not initially respond to α1-blocker or who strive to reduce these metabolic risk factors.

The mechanism of action of phosphodiesterase type 5 inhibitors in the treatment of lower urinary tract symptoms related to benign prostatic hyperplasia

CONTEXT

Clinical trials of phosphodiesterase type 5 inhibitors (PDE5-Is) have consistently demonstrated a significant reduction in lower urinary tract symptoms (LUTS) and small urinary flow rate changes in men with benign prostatic hyperplasia (BPH).

OBJECTIVE

This review presents the proposed mechanisms of action of PDE5-Is in the treatment of BPH-LUTS focusing on the localization of PDE5 isoenzymes in the pelvic structures; smooth muscle relaxation in the bladder, prostate, and supporting vasculature; increased blood perfusion of the bladder and prostate; and modulation of sensory impulses from these organs.

EVIDENCE ACQUISITION

Literature describing in vitro, preclinical, or clinical studies of pathologic processes contributing to LUTS or effects of PDE5 inhibition on the lower urinary tract (LUT) was selected for review.

EVIDENCE SYNTHESIS

We objectively assessed and summarized the published data focusing on articles published within the past 10 yr. Articles before the time cut-off were included if historically relevant.

CONCLUSIONS

The PDE5 isoenzymes are highly expressed in the LUT including the bladder, prostate, and their supporting vasculature. In vitro assays have demonstrated PDE5-Is by regulating cyclic guanosine monophosphate (cGMP) degradation and enhancing the nitric oxide/cGMP signaling pathway to relax human smooth muscle strips from the prostate, bladder, and LUT arteries. In animals characterized by ischemia/hypoxia of the genitourinary tract, treatment with PDE5-Is increases bladder and prostate tissue oxygenation. PDE5-Is have been shown to reduce nonvoiding contractions and bladder afferent nerve firing in decerebrate spinal cord-injured rats, and to reduce mechanosensitive afferent activities of both Aδ- and C-fibers in an irritated or overextended bladder model.

Tetrodotoxin- and resiniferatoxin-induced changes in paracervical ganglion ChAT- and nNOS-IR neurons supplying the urinary bladder in female pigs

The aim of the present study was to establish the effect of intravesical administration of resiniferatoxin (RTX) and tetrodotoxin (TTX) on the chemical coding of paracervical ganglion (PCG) neurons supplying the urinary bladder in the pig. In order to identify the PCG neurons innervating the bladder, retrograde tracer Fast Blue was injected into the bladder wall prior to intravesical RTX or TTX administration. Consequent application of immunocytochemical methods revealed that in the control group 76.82% of Fast Blue positive PCG neurons contain nitric oxide synthetase (nNOS), and 66.92% contain acetylcholine transferase (ChAT). Intravesical infusion of RTX resulted in a reduction of the nNOS-IR neurons to 57.74% and ChAT-IR to 57.05%. Alternative administration of TTX induced an increase of nNOS-IR neurons up to 79.29% and a reduction of the ChAT-IR population down to 3.73% of the Fast Blue positive PCG cells. Our data show that both neurotoxins affect the chemical coding of PCG cells supplying the porcine urinary bladder, but the effects of their action are different. Moreover, these results shed light on the possible involvement of NO-ergic and cholinergic neurons in the mechanisms of therapeutic action exerted by RTX and TTX in curing the overactive bladder disorder.

Are metabolic syndrome and its components associated with lower urinary tract symptoms? Results from a Chinese male population survey

OBJECTIVE

To investigate the association between severity of lower urinary tract symptoms (LUTS) and metabolic syndrome (MetS) and its components in a large male population in China.

METHODS

Data were collected from 3103 men attending the Fangchenggang Area Male Healthy and Examination Survey (FAMHES) from September 2009 to December 2009. LUTS were assessed by the International Prostate Symptom Score (IPSS) and MetS were defined using a modification of the Adult Treatment Panel III guidelines. Blood samples were drawn to determine serum lipids and glucose levels. Comprehensive information on demographic characteristics and medication was also collected through questionnaires. The association between LUTS and MetS was presented as odds ratios and 95% confidence intervals estimated using a logistic regression model.

RESULTS

The presence of MetS was not associated with the severity of LUTS (multivariate OR=0.97, 95% CI=0.67-1.39), but its subcategories of moderate or severe storage symptoms were inversely related to MetS (multivariate OR=0.64, 95% CI=0.44-0.91). Aging was observed to be a major risk factor for LUTS, such that men 60 years or older experienced 2-fold the odds of moderate or severe LUTS (OR=2.79, 95% CI=1.82-4.29) when compared with men 40 years or less). Component of MetS, such as systolic blood pressure, has increased odds for moderate or severe postmicturition symptoms but with no statistically significant results in multivariate analysis (multivariate OR=1.22, 95% CI=0.93-1. 60).

CONCLUSIONS

Our data suggest that the MetS is not associated with LUTS. However, for subcategory symptoms, decreased odds of MetS was observed in moderate or severe voiding storage symptoms.

Neurochemical plasticity of nitric oxide synthase isoforms in neurogenic detrusor overactivity after spinal cord injury

Nitric oxide (NO) participates in the neural pathways controlling the lower urinary tract (LUT). Expression of NO synthase (NOS) can be upregulated after spinal cord injury (SCI), and altered NOS activity may participate in resulting LUT dysfunction. To investigate distribution of NOS-immunoreactivity (NOS-IR) in neurons of rats following SCI and the possible effects of NOS inhibitors. Expression of neuronal and inducible NOS-IR in lumbosacral spinal cord was assessed in rats. Cystometry was performed to examine effects of intrathecal injection of NOS inhibitor. There was increased expression of neuronal NOS-IR after trauma. Maximum bladder capacity was increased by neuronal NOS (nNOS) inhibitors. Upregulation of nNOS may facilitate emergence of the spinal micturition reflex following SCI; nNOS inhibitor suppressed SCI-induced urinary incontinence by increasing bladder capacity. Our results indicate manipulation of NO production could help treat LUT dysfunction after SCI.

Cyclic nucleotide metabolism including nitric oxide and phosphodiesterase-related targets in the lower urinary tract

The clinical data on the use of the orally active phosphodiesterase (PDE) type 5 inhibitors sildenafil (VIAGRA™), vardenafil (LEVITRA™), and tadalafil (CIALIS™) for the treatment of male erectile dysfunction have boosted research activities on the physiology and pharmacology of the organs of the lower urinary tract (LUT). This includes both intracellular signal transduction in the prostate, urinary bladder (detrusor), and urethra, as well as central brain and spinal cord pathways controlling the function of the LUT. Such efforts provided the basis for the development of new therapeutic modalities into the management of dysfunctions/ syndromes of the LUT, some of which are already offered to the patients. The pharmacological treatment of the overactive bladder and the so-called benign prostatic syndrome, including LUT symptomatology and bladder outlet obstruction secondary to benign prostatic enlargement, has primarily focused on selective, orally available drugs acting by influencing intracellular regulatory mechanisms. These agents are regarded efficacious, have a fast onset of drug action in the target tissue and an improved effect-to-side-effect ratio. Better understanding of the functional significance of proteins related to cyclic nucleotide-dependent pathways, such as nitric oxide synthase, cytosolic and membrane-bound guanylyl cyclases, PDE isoenzymes and cyclic AMP- and cyclic GMP-binding protein kinases, the relative distribution in tissues of the LUT, and the consequences for urogenital function, seems to be of particular interest in order to identify new or more selective pharmacological approaches to manage disorders of the LUT. The present review focuses on cyclic nucleotide-related targets involved in the control of the function of the bladder, prostate, and urethra and the significance of those proteins in the process of evolving new pharmacological options for the treatment of LUT symptoms secondary to benign prostatic hyperplasia as well as dysfunctions of the storage and voiding capability of the urinary bladder.

Functional evidence of nitrergic neurotransmission in the human urinary bladder neck

Nitric oxide (NO) is involved in the non-adrenergic non-cholinergic (NANC) inhibitory neurotransmission of the lower urinary tract. However, functional evidence of this involvement in the human urinary bladder neck has not been consistently demonstrated. Therefore, the current study investigates the relaxations to endogenously released and/or exogenously added NO, in the human bladder neck. Urothelium-denuded bladder neck strips were dissected and mounted in isolated organ baths, containing a physiological saline solution (PSS) at 37 degrees C and continuously gassed with 5% CO(2) and 95% O(2), for isometric force recording. The relaxations to transmural nerve stimulation (EFS) or to exogenously applied NO, as an acidified solution of NaNO(2) were carried out on strips precontracted with phenylephrine, and treated with guanethidine and atropine, to block noradrenergic neurotransmission and muscarinic receptors, respectively. EFS (0.5-16Hz) and exogenous NaNO(2) (1muM to 1mM) evoked frequency- and concentration-dependent relaxations, respectively. The nerve responses were abolished by the blockade of neuronal voltage-activated Na(+) channels with tetrodotoxin, indicating their neurogenic character. N(G)-nitro-l-arginine (l-NOARG), a NO synthase inhibitor, abolished the relaxations to nerve stimulation, which were partially reversed by the substrate of NO synthesis l-arginine. l-NOARG failed to modify the relaxations to exogenous NaNO(2). These results suggest that NO is the major NANC inhibitory neurotransmitter in the human urinary bladder neck. Blockers of NO synthase could be useful in therapy for the urinary incontinence produced by intrinsic sphincteric deficiency.

Effects of tadalafil on lower urinary tract symptoms secondary to benign prostatic hyperplasia in men with or without erectile dysfunction

OBJECTIVES

To compare the safety and efficacy of the daily erectogenic therapy, tadalafil, on lower urinary tract symptoms secondary to benign prostatic hyperplasia (BPH-LUTS) in men with or without comorbid erectile dysfunction (ED).

METHODS

Following a 4-week placebo run-in period, men with moderate-to-severe BPH-LUTS were randomized to placebo or tadalafil 2.5, 5, 10, or 20 mg once daily for 12 weeks. International Prostate Symptom Scores (IPSS), IPSS quality of life, and BPH Impact Index were measured every 4 weeks. Safety was mainly assessed via spontaneous reports of adverse events. Data from men with (n=716) or without (n=340) ED at baseline were compared in posthoc analyses.

RESULTS

Men with ED were older and had more frequent hypertension, hyperlipidemia, coronary artery disease, and diabetes at baseline compared with men without ED. After 12 weeks, changes in IPSS in men with ED (least squares mean change from baseline, placebo: -2.4; tadalafil 2.5, 5, 10, 20 mg: -4.3, -4.8, -5.3, -5.6) and without ED (-2.4, -3.2, -5.3, -5.1, -4.5) were not significantly different (subgroup/interaction P values: .352/.644). Similar effects were observed for IPSS quality of life (with ED: -0.6, -0.9, -0.9, -1.0, -1.1; without ED: -0.6, -0.7, -0.9, -0.8, -0.8; 0.090/0.773) and BPH Impact Index (with ED: -0.7, -0.9, -1.3, -1.3, -1.4; without ED: -1.0, -0.7, -1.3, -1.3, -1.2; 0.753/0.852). Tadalafil was generally well tolerated, and men with or without ED had similar tolerability profiles.

CONCLUSIONS

Changes in BPH-LUTS after 12 weeks of treatment with placebo or various doses of once daily tadalafil were similar in men with or without comorbid ED.

Urodynamic effects of once daily tadalafil in men with lower urinary tract symptoms secondary to clinical benign prostatic hyperplasia: a randomized, placebo controlled 12-week clinical trial

PURPOSE

We explored the impact of once daily tadalafil on urodynamic measures in men with lower urinary tract symptoms secondary to clinical benign prostatic hyperplasia via invasive and noninvasive urodynamic studies.

MATERIALS AND METHODS

We conducted a multicenter, randomized, double blind, placebo controlled clinical trial comparing once daily tadalafil 20 mg vs placebo during 12 weeks in men with lower urinary tract symptoms secondary to clinical benign prostatic hyperplasia with or without bladder outlet obstruction. Invasive and noninvasive urodynamics, International Prostate Symptom Score and general safety were assessed. The primary study end point was change in detrusor pressure at maximum urinary flow rate.

RESULTS

Urodynamic measures remained largely unchanged during the study with no statistically significant or clinically adverse difference between tadalafil and placebo in change in detrusor pressure at maximum urinary flow rate (mean difference between treatments -2.2 cm H(2)O, p = 0.33) or any other urodynamic parameter assessed including maximum urinary flow rate, maximum detrusor pressure, bladder outlet obstruction index or bladder capacity (all measures p > or = 0.13). Treatment with tadalafil resulted in significant improvements in International Prostate Symptom Score (mean difference between treatments -4.2, p < 0.001). Tadalafil was generally well tolerated with the majority of adverse events being mild to moderate in severity and few patients discontinuing due to adverse events (tadalafil 2.0%, placebo 1.0%).

CONCLUSIONS

Treatment with tadalafil once daily for lower urinary tract symptoms secondary to clinical benign prostatic hyperplasia showed no negative impact on bladder function as measured by detrusor pressure at maximum urinary flow rate or on any other urodynamic parameter assessed. Nonetheless men receiving tadalafil reported significant improvements in International Prostate Symptom Score with an adverse events profile similar to other recent studies of tadalafil for lower urinary tract symptoms secondary to clinical benign prostatic hyperplasia.

Changes in peak urinary flow and voiding efficiency in men with signs and symptoms of benign prostatic hyperplasia during once daily tadalafil treatment

OBJECTIVE

To determine, by post hoc analysis, the effects of tadalafil (a long-acting phosphodiesterase 5 inhibitor) on peak urinary flow (Q(max)), bladder capacity, voiding efficiency and the obstructive symptoms of benign prostatic hyperplasia (BPH) in men with lower urinary tract symptoms secondary to BPH (BPH-LUTS), compared with placebo.

PATIENTS AND METHODS

After a 4-week placebo run-in period, 1058 men with BPH-LUTS were randomly allocated to receive once daily treatment with placebo or tadalafil (2.5, 5, 10, or 20 mg) for 12 weeks. Uroflowmetry, postvoid residual volume (PVR), and BPH symptom score measurements were assessed throughout the trial.

RESULTS

Increases in Q(max) were numerically greater for tadalafil (2.5, 5, 10, and 20 mg with percentage changes of 15%, 16%, 17%, 22%, respectively) vs placebo (12%), but did not reach statistical significance. Age, baseline Q(max), erectile dysfunction history, sexual activity, and previous alpha-blocker therapy significantly influenced the Q(max) response. Tadalafil was not associated with significant changes in PVR. Tadalafil had its greatest effects on bladder capacity and voiding efficiency in men with a Q(max) of <10 mL/s at baseline, but these changes were not significantly different from placebo responses. Tadalafil treatment significantly improved the IPSS obstructive subscores (tadalafil 2.5, 5, 10, 20 mg with percentage changes of 24%, 31%, 33%, 33%, respectively) vs placebo (13%).

CONCLUSIONS

Once daily tadalafil did not significantly change Q(max) or voiding efficiency compared with placebo in men with BPH-LUTS, although there were dose-dependent improvements. No subgroups were identified where tadalafil or placebo treatment had a deleterious effect on Q(max). Despite these minimal changes in uroflowmetric measures, tadalafil was associated with clinically meaningful and statistically significant improvements in the obstructive symptoms of BPH.

Pharmacologic responses of the mouse urinary bladder

The aim of the study was to determine pathways involved in contraction and relaxation of the mouse urinary bladder. Mouse bladder strips were set up in gassed Krebs-bicarbonate solution and responses to various drugs and electrical field stimulation were obtained. Isoprenaline (b-receptor agonist) caused a 63% inhibition of carbachol precontracted detrusor (EC50=2nM). Carbachol caused contraction (EC50=0.3µM), responses were antagonised more potently by 4-DAMP (M3-antagonist) than methoctramine (M2-antagonist). Electrical field stimulation caused contraction, which was inhibited by atropine (60%) and less by guanethidine and α,β-methylene-ATP. The neurogenic responses were not potentiated by inhibition of nitric oxide synthase. Presence of an intact urothelium significantly depressed responses to carbachol (p=0.02) and addition of indomethacin and L-NNA to remove prostaglandin and nitric oxide production respectively did not prevent the inhibitory effect of the urothelium. In conclusion, b-receptor agonists cause relaxation and muscarinic agonists cause contraction via the M3-receptor. Acetylcholine is the main neurotransmitter causing contraction while nitric oxide has a minor role. The mouse and human urothelium are similar in releasing a factor that inhibits contraction of the detrusor muscle which is unidentified but is not nitric oxide or a prostaglandin. Therefore, the mouse may be used as a model to study the lower urinary tract.

A possible relationship between testosterone and lower urinary tract symptoms in men

PURPOSE

In this study we searched for possible associations between serum testosterone levels and the severity of lower urinary tract symptoms in men.

MATERIALS AND METHODS

In 278 patients with a mean age of 62 years blood levels of total testosterone, albumin, sex hormone-binding globulin, fasting glucose, fasting insulin and high sensitivity C-reactive protein were measured. Free testosterone, bioavailable testosterone and homeostasis model assessment of insulin resistance were calculated. Prostate volume was measured by transrectal ultrasonography and the severity of lower urinary tract symptoms was assessed using the International Prostate Symptom Score.

RESULTS

Calculated free testosterone and bioavailable testosterone were negatively related to International Prostate Symptom Score total scores and subscores (voiding symptoms) after adjusting for age, prostate volume, high sensitivity C-reactive protein and homeostasis model assessment of insulin resistance (p <0.05). In addition, calculated free testosterone and bioavailable testosterone were significantly related to the presence of severe lower urinary tract symptoms (International Prostate Symptom Score 20 or greater) using unadjusted and adjusted models (p <0.05), although the odds ratio of bioavailable testosterone was lower than that of calculated free testosterone on multivariate analysis. High sensitivity C-reactive protein was negatively correlated with serum total testosterone (r = -0.128, p = 0.038) and bioavailable testosterone (r = -0.126, p = 0.041), and homeostasis model assessment of insulin resistance was negatively correlated with serum total testosterone (r = -0.236, p <0.001), calculated free testosterone (r = -0.179, p = 0.003) and bioavailable testosterone (r = -0.162, r = 0.007). However, no significant correlation was found between high sensitivity C-reactive protein or homeostasis model assessment of insulin resistance, and International Prostate Symptom Score total scores, voiding symptoms scores and storage symptoms scores.

CONCLUSIONS

Our findings support the favorable role of endogenous testosterone in lower urinary tract function and suggest that testosterone deficiency may be a pathophysiological mechanism connecting lower urinary tract symptoms and the metabolic syndrome in men.

Tadalafil administered once daily for lower urinary tract symptoms secondary to benign prostatic hyperplasia: a dose finding study

PURPOSE

Phosphodiesterase type 5 inhibitors are widely used to treat erectile dysfunction. Preliminary data have suggested phosphodiesterase type 5 inhibitor efficacy in men with lower urinary tract symptoms associated with clinical benign prostatic hyperplasia.

MATERIALS AND METHODS

After a 4-week placebo run-in period 1,058 men with benign prostatic hyperplasia lower urinary tract symptoms were randomly allocated to receive 12-week, once daily treatment with placebo or tadalafil (2.5, 5, 10 or 20 mg).

RESULTS

The International Prostate Symptom Score least squares mean change from baseline to end point was significantly improved for 2.5 (-3.9, p = 0.015), 5 (-4.9, p <0.001), 10 (-5.2, p <0.001) and 20 mg (-5.2, p <0.001) tadalafil compared to placebo (-2.3). International Prostate Symptom Score improvements at 4, 8 and 12 weeks were significant for all tadalafil doses and they demonstrated a dose-response relationship. Tadalafil (2.5 mg) significantly improved the International Prostate Symptom Score obstructive subscore and the International Index of Erectile Function-Erectile Function domain, the latter in sexually active men with a history of erectile dysfunction. Statistically significant improvements were noted for 5, 10 and 20 mg tadalafil compared to placebo, as assessed by the International Prostate Symptom Score irritative and obstructive subscores, International Prostate Symptom Score Quality of Life, Benign Prostatic Hyperplasia Impact Index (nonsignificant for 10 mg), Global Assessment Question and International Index of Erectile Function-Erectile Function domain. No statistically significant effect of treatment compared to placebo was noted for peak flow at any tadalafil dose. Treatment emergent adverse events were infrequent in all tadalafil groups.

CONCLUSIONS

Once daily tadalafil demonstrated clinically meaningful and statistically significant efficacy and it was well tolerated in men with benign prostatic hyperplasia lower urinary tract symptoms. Of the doses studied 5 mg tadalafil appeared to provide a positive risk-benefit profile.

Androgens and bladder outlet obstruction: a correlation with pressure-flow variables in a preliminary study

OBJECTIVES

To determine the relationship between androgens, lower urinary tract symptoms (LUTS) and urodynamic variables of bladder outlet obstruction (BOO) in patients with LUTS/benign prostatic hyperplasia (BPH), as androgens are important in the pathogenesis of LUTS.

PATIENTS AND METHODS

Twenty-five men with symptomatic BPH were enrolled in the study and had a complete urodynamic investigation, establishing BOO. Age, prostate-specific antigen level, prostate volume and postvoid residual volume were recorded and the International Prostate Symptom Score (IPSS) was estimated. Detrusor pressure at maximum flow (P(det)Q(max)), at urethral closure (P(det)Cl, the pressure at the end of urinary flow) and maximum detrusor pressure (P(detmax)) was recorded, while detrusor overactivity (DO) was noted when present. Blood samples were collected to measure total testosterone (T), and free T (FT) was calculated. Patients were grouped according to FT levels as low (<72 pg/mL) and normal (FT > or =72 pg/mL).

RESULTS

Ten patients had a low FT level, with a mean (sd) of 54.3 (16.5) pg/mL, and 15 a normal level of FT, of 90.5 (11) pg/mL. FT was negatively correlated with P(det)Cl, and P(det)Q(max); the mean P(det)Cl and P(det)Q(max) differed significantly between patients with low and normal FT levels. Fourteen patients had DO and they had significantly lower levels of FT than those with no DO. All patients with a FT level of <60 pg/mL had DO, and the presence of instability differed significantly from the rest of the group.

CONCLUSIONS

Low T levels in clinical BOO correlated negatively with P(det)Cl and P(det)Q(max), while promoting DO. Androgen seems to have an ameliorating role in lower urinary tract function.

Role of neuronal voltage-gated K(+) channels in the modulation of the nitrergic neurotransmission of the pig urinary bladder neck

BACKGROUND AND PURPOSE

As nitric oxide (NO) plays an essential role in the inhibitory neurotransmission of the bladder neck of several species, the current study investigates the mechanisms underlying the NO-induced relaxations in the pig urinary bladder neck.

EXPERIMENTAL APPROACH

Urothelium-denuded bladder neck strips were dissected and mounted in isolated organ baths containing a physiological saline solution at 37 degrees C and continuously gassed with 5% CO(2) and 95% O(2), for isometric force recording. The relaxations to transmural nerve stimulation (EFS), or to exogenously applied acidified NaNO(2) solution were carried out on strips pre-contracted with phenylephrine, and treated with guanethidine and atropine, to block noradrenergic neurotransmission and muscarinic receptors, respectively.

KEY RESULTS

EFS (0.2-1 Hz) and addition of acidified NaNO(2) solution (1 microM-1 mM) evoked frequency- and concentration-dependent relaxations, respectively. These responses were potently reduced by the blockade of guanylate cyclase and were not modified by the K(+) channel blockers iberiotoxin, charybdotoxin, apamin or glibenclamide. The voltage-gated K(+) (Kv) channels inhibitor 4-aminopyridine, greatly enhanced the nitrergic relaxations evoked by EFS, but did not affect the NaNO(2) solution-induced relaxations.

CONCLUSIONS AND IMPLICATIONS

NO, whose release is modulated by pre-junctional Kv channels, relaxes the pig urinary bladder neck through a mechanism dependent on the activation of guanylate cyclase, in which post-junctional K(+) channels do not seem to be involved. Modulation of Kv channels could be useful in the therapy of the urinary incontinence produced by intrinsic sphincteric deficiency.

Effects of phosphodiesterase type 5 inhibitor on the contractility of prostate tissues and urethral pressure responses in a rat model of benign prostate hyperplasia

AIM

This study was performed to investigate the effect of DA-8159, a selective phosphodiesterase 5 (PDE5) inhibitor, on benign prostatic hyperplasia (BPH) both in vitro and in vivo.

METHODS

We assessed the influence of DA-8159 on the contractility of rat prostate tissues in an organ-bath experiment. In addition, in order to investigate whether chronic administration of DA-8159 prevents the increase of electrostimulation-induced intraurethral pressure (IUP) responses associated with BPH, BPH was induced by steroid hormones (testosterone plus 17beta-estradiol) and DA-8159 (5, 20 mg/kg) was concomitantly administered once a day for 8 weeks. After that the electrostimulation-induced IUP responses were measured. Finally, we investigated the acute treatment effect of DA-8159 on IUP responses in an established BPH model after a single intravenous injection of DA-8159 (0.3, 1 mg/kg).

RESULTS

DA-8159 concentration-dependently reduced the contraction of the isolated prostate strips with an IC50 value of 70 microM. In chronic treatment study, while the BPH control rats showed a significantly increased IUP both at the baseline and by electrostimulation, the chronic DA-8159 treatment significantly attenuated the increase in IUP responses in a dose- and frequency-dependent manner. In the acute treatment study, a single intravenous injection of DA-8159 also prevented the increase in urethral pressure in a dose-dependent manner.

CONCLUSIONS

These results suggest that DA-8159 may be beneficial on lowering the urethral pressure associated with BPH via dilatation of the prostate, but a further evaluation of the efficacy on humans needs to be performed.

Pre-junctional alpha2-adrenoceptors modulation of the nitrergic transmission in the pig urinary bladder neck

AIMS

To investigate the nitric oxide (NO)-mediated nerve relaxation and its possible modulation by pre-junctional alpha2-adrenoceptors in the pig urinary bladder neck.

METHODS

Urothelium-denuded bladder neck strips were dissected, and mounted in isolated organ baths containing a physiological saline solution (PSS) at 37 degrees C and continuously gassed with 5% CO2 and 95% O2, for isometric force recording. The relaxations to transmural nerve stimulation (electrical field stimulation [EFS]) or exogenously applied NO were carried out on strips pre-contracted with 1 microM phenylephrine (PhE) and treated with guanethidine (10 microM) and atropine (0.1 microM), to block noradrenergic neurotransmission and muscarinic receptors, respectively.

RESULTS

EFS (0.2-1 Hz, 1 msec duration, 20 sec trains, current output adjusted to 75 mA) evoked frequency-dependent relaxations which were abolished by the neuronal voltage-activated Na+ channel blocker tetrodotoxin (TTX, 1 microM). These responses were potently reduced by the nitric oxide synthase (NOS) inhibitor NG-nitro-L-arginine (L-NOARG, 30 microM) and further reversed by the NO synthesis substrate L-arginine (L-ARG, 3 mM). The alpha2-adrenoceptor agonist BHT-920 (2 microM) reduced the electrically evoked relaxations, its effectiveness being higher on the responses induced by low frequency stimulation. BHT-920-elicited reductions were fully reversed by the alpha2-adrenoceptor antagonist rauwolscine (RAW, 1 microM). Exogenous NO (1 microM-1 mM) induced concentration-dependent relaxations which were not modified by BHT-920, thus eliminating a possible post-junctional modulation.

CONCLUSIONS

These results indicate that NO is involved in the non-adrenergic non-cholinergic (NANC) inhibitory neurotransmission in the pig urinary bladder neck, the release of NO from intramural nerves being modulated by pre-junctional alpha2-adrenoceptor stimulation.

Systemic Nitric Oxide Augmentation Leads to a Rapid Decrease of the Bladder Outlet Resistance in Healthy Men

OBJECTIVE

We examined the immediate effect of a systemic nitric oxide augmentation on the bladder outlet resistance in healthy men.

METHODS

Eleven healthy male volunteers with a mean age of 25.5 yr were included in the study. They were prepared for a standard urodynamic study, and a baseline pressure-flow study was obtained. The subjects were then given 20 mg isosorbide dinitrate sublingually, and after refilling their bladder a second pressure-flow study was done after 20 min. The pressure-flow studies were then compared in regard to the average flow rate, the average detrusor pressure during micturition, and the detrusor pressure at maximum flow rate.

RESULTS

One of the subjects was unable to void and had to be excluded from the study. In the remaining 10 men, the mean average flow rate increased from 16.7 ml/s before to 20.2 ml/s after the intake of the NO donor (P=0.013). Concomitantly, the average detrusor pressure during micturition decreased from a mean of 57 to 52 cm H2O (P=0.004) and the mean detrusor pressure at maximum flow rate decreased from 60 to 52 cm H2O (P=0.013).

CONCLUSIONS

Systemic NO augmentation can lower the functional bladder outlet resistance very rapidly in men. Our results support the concept that the NO-cGMP pathway may be a promising target for medical treatment of lower urinary tract symptoms.

Systemic Augmentation of Nitric Oxide: Is There an Immediate Effect on the Urinary Flow Rate in Healthy Men?

INTRODUCTION

Nitric oxide (NO) is an important neurotransmitter in the lower urinary tract. Data from experimental studies in animals and humans suggest that NO donors like isosorbide dinitrate could be used to lower the infravesical resistance. Despite the potentially significant clinical benefit of such an effect, it has hardly been studied in vivo in men. We investigated the immediate effect of isosorbide dinitrate on the urinary flow rate and the functional bladder capacity in healthy young men.

PATIENTS AND METHODS

A free urinary flow was measured in 20 healthy male volunteers on two consecutive micturitions. 15-25 min prior to the second micturition, 10 mg of the NO donor isosorbide dinitrate was administered sublingually.

RESULTS

We found no significant difference between baseline measurement and the micturition after NO administration with regard to the totally voided volume, the maximal or the average flow rate as well as the flow rate corrected for the voided volume.

CONCLUSION

Systemic augmentation of NO does not produce a relevant immediate effect on the urinary flow rate or the functional bladder capacity in healthy men.

Nitric oxide/cGMP-mediated effects in the outflow region of the lower urinary tract--is there a basis for pharmacological targeting of cGMP?

Treatment with alpha-adrenoceptor antagonists that reduce the tone of prostatic stromal and urethral smooth muscle has beneficial effects in patients with benign prostatic hyperplasia (BPH) and lower urinary tracts symptoms (LUTS) and has brought attention to regulatory mechanisms of smooth muscle contractility of the outflow region. The prostate, urethra and bladder neck are densely supplied by nitric oxide (NO)-synthase-containing nerves that cause relaxation upon activation. In various experimental models, altered function or activity of the NO/cGMP pathway of the bladder neck and urethra may be related to inappropriate or un-coordinated functions of the bladder outlet and detrusor, but causal connections between alterations in this signaling system, a dysfunctional bladder outlet, and the development of LUTS are not established for humans. The present review focuses on regulatory functions of smooth muscle contractility by the NO/cGMP-pathway in the bladder neck, urethra, and prostate. Disease-related alterations in the NO/cGMP-pathway, and putative options for pharmacological modification of this signaling pathway in the out-flow region are briefly discussed.

Pharmacology of the lower urinary tract: basis for current and future treatments of urinary incontinence

The lower urinary tract constitutes a functional unit controlled by a complex interplay between the central and peripheral nervous systems and local regulatory factors. In the adult, micturition is controlled by a spinobulbospinal reflex, which is under suprapontine control. Several central nervous system transmitters can modulate voiding, as well as, potentially, drugs affecting voiding; for example, noradrenaline, GABA, or dopamine receptors and mechanisms may be therapeutically useful. Peripherally, lower urinary tract function is dependent on the concerted action of the smooth and striated muscles of the urinary bladder, urethra, and periurethral region. Various neurotransmitters, including acetylcholine, noradrenaline, adenosine triphosphate, nitric oxide, and neuropeptides, have been implicated in this neural regulation. Muscarinic receptors mediate normal bladder contraction as well as at least the main part of contraction in the overactive bladder. Disorders of micturition can roughly be classified as disturbances of storage or disturbances of emptying. Failure to store urine may lead to various forms of incontinence, the main forms of which are urge and stress incontinence. The etiology and pathophysiology of these disorders remain incompletely known, which is reflected in the fact that current drug treatment includes a relatively small number of more or less well-documented alternatives. Antimuscarinics are the main-stay of pharmacological treatment of the overactive bladder syndrome, which is characterized by urgency, frequency, and urge incontinence. Accepted drug treatments of stress incontinence are currently scarce, but new alternatives are emerging. New targets for control of micturition are being defined, but further research is needed to advance the pharmacological treatment of micturition disorders.

Regional differences in nitrergic neuronal density in the developing porcine urinary bladder

Nitric oxide (NO) is involved in normal bladder physiology by regulating local arteriolar tone and smooth muscle relaxation and modulating the production of extracellular matrix proteins in vitro. Little information is available regarding the nitrergic innervation of the bladder during development. In this study we investigated the changes in density and morphology of the intramural nitrergic neurons of the porcine urinary bladder during development using whole-mount preparation. Bladder specimens were obtained from porcine foetuses of gestational age 60 days (n=5) and 90 days (n=5) and from newborn piglets (n=5) after perfusion fixation. Bladders were divided into base, body, and dome. Whole-mount preparation using NADPH-diaphorase (NADPH-d) histochemistry was used to visualize nitrergic innervation of the urinary bladders and to measure density of NADPH-positive ganglia (including single neurons), number of NADPH-d positive neurons per ganglion, and size of individual neurons. One-way ANOVA and chi-square tests were used for statistical analysis with a p-value <0.05 considered statistically significant. NADPH-d positive ganglia were numerous in the muscular layer of all three age groups. At E60, ganglion density was significantly higher in the body (mean 880/cm(2)) than in the dome (397/cm(2)) or the base (676/cm(2)). The ganglion density significantly decreased with age. The number of NADPH-d positive neurons per ganglion increased significantly between E90 and birth (p<0.01). A marked increase in the size of individual neurons over time was also seen (p<0.001), predominantly due to an increase in cytoplasm. Our data on whole-mount preparations demonstrate that significant maturation in nitrergic neuronal density and morphology occurs in the porcine urinary bladder, at least until birth.

Urinary bladder contraction and relaxation: physiology and pathophysiology

The detrusor smooth muscle is the main muscle component of the urinary bladder wall. Its ability to contract over a large length interval and to relax determines the bladder function during filling and micturition. These processes are regulated by several external nervous and hormonal control systems, and the detrusor contains multiple receptors and signaling pathways. Functional changes of the detrusor can be found in several clinically important conditions, e.g., lower urinary tract symptoms (LUTS) and bladder outlet obstruction. The aim of this review is to summarize and synthesize basic information and recent advances in the understanding of the properties of the detrusor smooth muscle, its contractile system, cellular signaling, membrane properties, and cellular receptors. Alterations in these systems in pathological conditions of the bladder wall are described, and some areas for future research are suggested.

The effect of nitric oxide on the resting tone and the contractile behaviour of the external urethral sphincter: a functional urodynamic study in healthy humans

AIMS

This functional urodynamic study assessed the effect of the nitric oxide donor isosorbide dinitrate on the external urethral sphincter and hypothesised first that nitric oxide could lower the resting sphincter pressure, second that nitric oxide could influence the sphincter contractility during magnetic stimulation, and third that nitric oxide could induce a faster external urethral sphincter fatigue during continuous magnetic stimulation.

METHODS

Eight healthy males gave their written informed consent and were included. A 2-channel microtip pressure transducer catheter was inserted into the urethra measuring the bladder and the external urethral sphincter pressure. Magnetic stimulation of the sacral roots was performed to evoke reproducible contractions of the external urethral sphincter. The baseline protocol included six single pulse stimulations and three stimulations 10sec in duration each for two frequencies 5Hz and 50Hz with intensities at the motor threshold of the pelvic floor. Then the subjects received 10 mg of isosorbide nitrate sublingually and the protocol was repeated 5min, 20min, 40min and 60min after drug administration.

RESULTS

The sublingual administration of isosorbide dinitrate could significantly reduce the resting pressure of the external urethral sphincter for at least one hour. The maximal contractile strength measured as the maximal urethral pressure during single pulse and continuous magnetic stimulation of the sacral roots also decreased significantly. Nitric oxide did not induce a significantly faster fatigue of the external urethral sphincter during continuous magnetic stimulation of the sacral roots.

CONCLUSIONS

This study shows a functionally relevant effect of nitric oxide on the resting tone and the contractile behaviour of the human external urethral sphincter in vivo while the fatigue properties did not changed significantly. Nitric oxide donors could offer a new pharmacological approach to treat urinary retention due to overactive or non-relaxing external urethral sphincter.

In vivo transfer of a neuronal nitric oxide synthase expression vector into the rat bladder by electroporation

OBJECTIVE

To investigate the possibility of in vivo gene transfer by attempting to transfer the neuronal nitric oxide synthase (nNOS) gene into rat bladder using electroporation.

MATERIALS AND METHODS

The bladder was exposed through an abdominal midline incision in 8-week-old male rats. Plasmid DNA of the marker genes green fluorescent protein (GFP) and luciferase, and the nNOS gene, was then injected into the subserosal space of the bladder and electroporation applied. At 72 h after gene transfer, GFP and luciferase were assayed in the isolated bladder and immunohistochemical staining used to detect nNOS; NO(x) released from isolated bladder strips was also assessed using microdialysis and high-performance liquid chromatography.

RESULTS

From the luciferase assay, 45 V, 1 Hz, 50 ms and eight pulses were selected as the optimum conditions for electroporation. Bladder specimens with GFP genes injected by electroporation showed bright and numerous sites of GFP expression in the smooth muscle layer. In rats with the nNOS gene injected by electroporation there was marked nNOS immunoreactivity, and NO(x) released from bladder strips was significantly greater than in the control groups.

CONCLUSIONS

These results suggest that electroporation is a useful technique for in vivo gene transfer into rat bladder smooth muscles, and that the nNOS gene transferred by this procedure functionally expresses and contributes to NO production.

The effect of intravesical sodium nitroprusside on idiopathic detrusor overactivity

Although nitric oxide (NO) plays an important role in the urethra and outlet region of the bladder, the role of this inhibitory neurotransmitter in the human detrusor remains unclear. We conducted a prospective, randomised, open study on 31 patients with urodynamically proven idiopathic detrusor overactivity in order to examine the effects of intravesical administration of the NO donor sodium nitroprusside (SNP) on detrusor overactivity. Thirty-one consecutive patients (14 male, 17 female; mean age 53.0+/-2.7 years) with idiopathic detrusor overactivity diagnosed by pressure-flow analysis were included in this study. The patients were randomised into two groups. Cystometries were performed with normal saline in the control group ( n=10) and with 7.2 mM SNP solution (2.16 mg/ml) in the study group ( n=21). We urodynamically investigated sensation, maximal cystometric capacity, compliance, instability index, amplitude and frequency of involuntary contractions. No statistically significant differences was found between the first (pressure-flow) and second (saline or SNP cystometry) urodynamic values in the control and study groups (P>0.05). We have demonstrated that SNP does not have any effect on uninhibited bladder contractions. These results suggest that the intravesical administration of SNP is not an effective treatment for detrusor overactivity.

[Regulation by autonomic nerves of bladder neck sphincter function--mainly on inhibitory NANC nerves]

This article describes current information concerning analyses of contraction and relaxation associated with electrical stimulation of efferent nerves in isolated mammalian sphincter muscles. Contractile responses of sphincters are mediated by alpha 1-adrenoceptors and muscarinic receptors stimulated by transmitters from adrenergic and cholinergic nerves, respectively, whereas those of the bladder body are almost exclusively mediated by transmitters from parasympathetic nerves. Relaxant responses to nerve stimulation are ascribed mainly to mechanisms that are sensitive and resistant to nitric oxide (NO) synthase inhibitors. Neurogenic calcitonin gene-related peptide and beta-adrenoceptor activation by neurogenic norepinephrine may also be involved in some mammals. Stimulus frequency is an important determinant to distinguish NO synthase-sensitive and -resistant components; responses at low frequencies are abolished by the enzyme inhibitors, whereas those at high frequencies are inhibited only partially. High and low frequency stimulation increases the cyclic GMP content in muscles, suggesting the involvement of neurogenic NO, although relaxation at high frequencies is only partially due to such a mechanism. From pharmacological studies so far analyzed, including ours performed with porcine urinary tract sphincters, it is concluded that NO synthase resistant-relaxation is not mediated by peptides nor compounds that open K+ channels in muscle cell membrane and stimulate beta-adrenoceptors. Contribution of NO and non-NO relaxing factor (s) in relaxant responses varies with animal species. Identification of this factor, determination of intracellular signaling processes and interaction with the NO/cyclic GMP system may give us a clue in developing new therapeutics to treat dysfunctions of the lower urinary tract sphincters.

Sphincterotomy and the treatment of detrusor-sphincter dyssynergia: current status, future prospects

STUDY DESIGN

Literature review of current treatment options for detrusor-sphincter dyssynergia (DSD) in spinal cord injury.

OBJECTIVES

To review the outcomes and complications associated with external sphincterotomy and to summarise the results and complications of alternative treatment options for detrusor-sphincter dyssynergia in spinal cord injury. In addition, we propose a potential alternative future drug treatment for external sphincter dyssynergia based upon recent research on the neuropharmacology of the external urethral sphincter.

SETTING

The National Spinal Injuries Centre, Stoke Mandeville Hospital, Aylesbury, UK.

METHODS

Medline search from 1966 to 2002 using the words 'external sphincterotomy', 'detrusor-sphincter dyssynergia' and 'neurogenic bladder combined with surgery'.

RESULTS

While external sphincterotomy is an effective treatment for DSD, a significant number of men following this procedure continue to have high intrarenal pressures, recurrent urinary infection or troublesome autonomic dysreflexia and a worryingly high proportion demonstrate persistently raised leak point pressures, putting them at subsequent risk of renal damage. Alternative treatments for external sphincter dyssynergia include urethral stents and balloon dilatation, both of which are effective. However, over the long term stents can undergo encrustation and there remains a definite risk of stent migration necessitating stent removal or replacement. Balloon dilatation of the external sphincter is associated with a risk of subsequent stricture formation. Intraurethral Botulinum A toxin seems to be effective though there have been no large randomised studies comparing it against placebo. However, it is not a durable treatment option and it has not found a common place in the treatment of DSD. There is now a considerable amount of experimental data from both animal and human studies to suggest that nitric oxide (NO) is an important physiological inhibitory neurotransmitter in the urethral sphincter, mediating relaxation of the external urethral sphincter. The potential role of sphincter NO augmentation for treatment of DSD is discussed.

CONCLUSION

External sphincterotomy remains the mainstay of treatment for urodynamically significant detrusor-sphincter dyssynergia, but in recent years a number of effective, alternative treatment options have become available. While at present there is no effective systemic drug treatment, recent research into external sphincter neuropharmacology suggests that systemic or topical augmentation of external sphincter NO may provide an effective method for lowering sphincter pressure.

Different distribution of nitric oxide synthase and soluble guanylyl cyclase activities in the detrusor and proximal urethra of the rabbit

PURPOSE

We investigated the different distributions of nitric oxide synthase (NOS) and soluble guanylate cyclase activities in the detrusor and proximal urethra in the rabbit.

MATERIALS AND METHODS

The detrusor and proximal urethra were excised, the mucosa and muscularis were separated and each layer was homogenized to measure the activities of NOS as well as baseline and sodium nitroprusside (SNP) activated soluble guanylate cyclase. Isometric tension experiments were performed in detrusor and urethral strips with and without mucosa.

RESULTS

In the detrusor NOS and sodium nitroprusside activated soluble guanylate cyclase activities in the mucosa were much higher than in the muscularis. While in the proximal urethra NOS activity in the 2 layers was similar, SNP activated soluble guanylate cyclase activity in the muscularis was 2.8 times higher than in the mucosa. Removing the mucosa reduced nitric oxide (NO) mediated neurogenic relaxation in the proximal urethra, while no relaxation responses could be elicited by electrical field stimulation with or without mucosa in the detrusor. On the other hand, removing the mucosa did not affect SNP or 8-bromo-cyclic guanosine monophosphate induced relaxation in the detrusor and proximal urethra.

CONCLUSIONS

In the detrusor NOS and soluble guanylate cyclase activities were mainly detected in the mucosa, while in the urethra these activities were distributed throughout the mucosa and muscularis. Also, the mucosa in the urethra but not in the detrusor contributed to electrical field stimulation induced, NO mediated relaxation. These findings confirm previous studies demonstrating that NO has a different role in the detrusor than in the proximal urethra.

Beta-adrenoceptor agonists stimulate endothelial nitric oxide synthase in rat urinary bladder urothelial cells

We have investigated the intracellular signaling mechanisms underlying the release of nitric oxide (NO) evoked by beta-adrenoceptor (AR) agonists in urinary bladder strips and cultured bladder urothelial cells from adult rats. Reverse transcription-PCR revealed that inducible NO synthase and endothelial NOS but not neuronal NOS genes were expressed in urothelial cells. NO release from both urothelial cells and bladder strips was decreased (37-42%) in the absence of extracellular Ca2+ (100 microm EGTA) and was ablated after incubation with BAPTA-AM (5 microm) or caffeine (10 mm), indicating that the NO production is mediated in part by intracellular calcium stores. NO release was reduced (18-24%) by nifedipine (10 microm) and potentiated (29-32%) by incubation with the Ca2+ channel opener BAYK8644 (1-10 microm). In addition, beta-AR-evoked NO release (isoproterenol; dobutamine; terbutaline; 10(-9) to 10(-5) m) was blocked by the NOS inhibitors N(G)-nitro-L-arginine methyl ester (30 microm) or N(G)-monomethyl-L-arginine (50 microm), by beta-adrenoceptor antagonists (propranol, beta1/beta2; atenolol, beta1; ICI 118551; beta2; 100 microm), or by the calmodulin antagonist trifluoperazine (50 microm). Incubating cells with the nonhydrolyzable GTP analog GTPgammaS (1 microm) or the membrane-permeant cAMP analog dibutyryl-cAMP (10-100 microm) directly evoked NO release. Forskolin (10 microm) or the phosphodiesterase IBMX (50 microm) enhanced (39-42%) agonist-evoked NO release. These results indicate that beta-adrenoceptor stimulation activates the adenylate cyclase pathway in bladder epithelial cells and initiates an increase in intracellular Ca2+ that triggers NO production and release. These findings are considered in light of recent reports that urothelial cells may exhibit a number of "neuron-like" properties, including the expression of receptors/ion channels similar to those found in sensory neurons.