Nitric oxide based influence of nitrates on micturition in patients with benign prostatic hyperplasia

Early investigational agents for the treatment of benign prostatic hyperplasia'

INTRODUCTION

Benign prostatic hyperplasia (BPH), as a clinical entity that affects many people, has always been in the forefront of interest among researchers, pharmaceutical companies, and physicians. Patients with BPH exhibit a diverse range of symptoms, while current treatment options can occasionally cause adverse events. All the aforementioned have led to an increased demand for more effective treatment options.

AREAS COVERED

This review summarizes the outcomes of new medications used in a pre-clinical and clinical setting for the management of male lower urinary tract symptoms (LUTS)/BPH and provides information about ongoing trials and future directions in the management of this condition. More specifically, sheds light upon drug categories, such as reductase‑adrenoceptor antagonists, drugs interfering with the nitric oxide (NO)/cyclic guanosine monophosphate (GMP) signaling pathway, onabotulinumtoxinA, vitamin D3 (calcitriol) analogues, selective cannabinoid (CB) receptor agonists, talaporfin sodium, inhibitor of transforming growth factor beta 1 (TGF-β1), drugs targeting the hormonal control of the prostate, phytotherapy, and many more.

EXPERT OPINION

Clinical trials are being conducted on a number of new medications that may emerge as effective therapeutic alternatives in the coming years.

Emerging drugs to target lower urinary tract symptomatology (LUTS)/benign prostatic hyperplasia (BPH): focus on the prostate

OBJECTIVES

The benign prostatic syndrome, comprising lower urinary tract symptomatology secondary to benign prostatic hyperplasia/enlargement, represents a major health care issue in westernized countries. The pharmacological management involves alpha-adrenoceptor antagonists, intervention into the hormonal control of prostate growth using inhibitors of the enzyme 5-alpha-reductase, and stimulation of the nitric oxide/cyclic GMP pathway by tadalafil, an inhibitor of the phosphodiesterase type 5.

METHODS

This review summarizes the achievements which have been made in the development of drug candidates assumed to offer opportunities as beneficial treatment options in the management of the benign prostatic syndrome.

RESULTS

A review of the literature has revealed that the line of development is focusing on drugs interfering with peripheral neuromuscular/neuronal mechanisms (nitric oxide donor drugs, agonists/antagonists of endogenous peptides, botulinum toxin, NX-1207), the steroidal axis (cetrorelix) or the metabolic turn-over (lonidamine), as well as the combination of drugs already established in the treatment of lower urinary tract symptomatology/benign prostatic hyperplasia (phosphodiesterase 5 inhibitor plus alpha-adrenoceptor antagonist).

CONCLUSION

Many research efforts have provided the basis for the development of new therapeutic modalities for the management of lower urinary tract dysfunctions, some of which might be offered to the patients in the near future.

Generation and Regulation of Spontaneous Contractions in the Prostate

Spontaneous myogenic contractions have been shown to be significantly upregulated in prostate tissue collected from men with Benign Prostatic Hyperplasia (BPH), an extremely common disorder of the ageing male. Although originally thought likely to be involved in 'housekeeping' functions, mixing prostatic secretions to prevent stagnation, these spontaneous myogenic contractions provide a novel opportunity to understand and treat BPH. This treatment potential differs from previous models, which focused exclusively on attenuating nerve-mediated neurogenic contractions. Previous studies in the rodent prostate have provided an insight into the mechanisms underlying the regulation of myogenic contractions. 'Prostatic Interstitial Cells' (PICs) within the prostate appear to generate pacemaker potentials, which arise from the summation of number of spontaneous transient depolarisations triggered by the spontaneous release of Ca²⁺ from internal stores and the opening of Ca²⁺-activated Cl^- channels. Pacemaker potentials then conduct into neighbouring smooth muscle cells to generate spontaneous slow waves. These slow waves trigger the firing of 'spike-like' action potentials, Ca²⁺ entry and contraction, which are not attenuated by blockers of neurotransmission. However, these spontaneous prostatic contractions can be modulated by the autonomic nervous system. Here, we discuss the mechanisms underlying rodent and human prostate myogenic contractions and the actions of existing and novel pharmacotherapies for the treatment of BPH. Understanding the generation of human prostatic smooth muscle tone will confirm the mechanism of action of existing drugs, inform the identification and effectiveness of new pharmacotherapies, as well as predict patient outcomes.

Drug Concentration in Rat Plasma, Bladder, and Prostate After Mirodenafil Administration in a Chronic Pelvic Ischemia Model

OBJECTIVE

To evaluate the distribution of a daily phosphodiesterase type 5 inhibitor dose (mirodenafil) in rat plasma and bladder and prostate tissue in a model of atherosclerosis-induced chronic pelvic ischemia.

METHODS

Thirty-two 18-week-old male Sprague Dawley rats were divided into two groups. Group I (n = 16) comprised a chronic pelvic ischemia model treated with mirodenafil and group II (n = 16) comprised a sham-operated model also treated with mirodenafil. The mirodenafil concentrations in each organ were measured at specific time points after 14 days of daily mirodenafil administration. The drug distribution ratio of group I to group II of each organ was measured, and the bladder tissue-to-plasma and prostate tissue-to-plasma ratios were calculated.

RESULTS

The mean drug concentration in the bladder of the rats in group I did not differ significantly from that of group II after mirodenafil administration. In the prostate, the mean drug concentration of group I was significantly higher than that of group II at 1 and 4 hours after drug administration. The drug concentration was higher in the bladder tissue than in the prostate tissue and the bladder tissue-to-plasma ratio was significantly higher than the prostate tissue-to-plasma ratio.

CONCLUSION

Our results suggest that mirodenafil levels might be sufficient in the target tissue after daily treatment in an ischemia-induced aging model. Considering the difficulties of tissue distribution study in human subjects, the results of this investigation provided meaningful evidence of the application of daily doses of mirodenafil for treating lower urinary tract symptoms in an aging population.

The Investigation of Relationship between Coronary Artery Ectasia, Benign Prostatic Enlargement, and Lower Urinary Tract Symptoms

OBJECTIVE

To investigate benign prostatic enlargement (BPE) and lower urinary tract symptoms (LUTS) in patients with coronary artery ectasia (CAE). The relation between CAE, BPE, and LUTS has not been studied so far.

METHODS

We investigated BPE and LUTS symptoms in 47 men with CAE, 45 men with coronary artery disease (CAD), and 47 male controls with normal coronary arteries. LUTS was evaluated by the International Prostate Symptom Score (IPSS). BPE was evaluated with transabdominal ultrasonography. CAD was defined as myocardial infarction and angiographically diagnosed coronary disease. CAE was defined as being without any stenotic lesions with a visual assessment of the coronary arteries showing a luminal dilatation ≥1.5 fold of the adjacent normal coronary segments.

RESULTS

Prostate volume was higher in CAE and CAD patients compared with that of the control subjects, respectively (41.0 ± 10.4 vs 33.5 ± 9.4 cm(3); 39.1 ± 10.3 vs 33.5 ± 9.4 cm(3); P = .0001); total IPSS was higher in CAD and CAE patients compared with that of the control subjects (P = .0001). Postmictional residual urine volume was higher in CAE and CAD patients compared with that of the control subjects (P = .002).

CONCLUSION

We showed that patients with CAE have higher prostate volume, IPSS, and postmictional residual urine volume compared with those of controls with normal coronary angiograms. This study proposes that BPE, LUTS, and CAE maybe different disorders to a common vascular pathology and endothelial dysfunction. This study showed that BPE and LUTS were frequently seen in CAE at least as much as in CAD. Therefore, LUTS and BPE should be kept in mind for CAE patients in follow-ups.

Protective effect of tadalafil on the functional and structural changes of the rat ventral prostate caused by chronic pelvic ischemia

BACKGROUND

The etiology of Benign Prostatic Hyperplasia (BPH), a common among aged men, is not fully understood, however, in addition to androgens and aging, chronic ischemia has been proposed to contribute. Using an established rat model, we investigated whether chronic ischemia alters the structural and functional properties of the ventral rat prostate, and whether phosphodiesterase type 5 (PDE5) inhibitor (tadalafil) may have a protective action.

METHODS

Adult male Sprague-Dawley rats were divided into control, arterial endothelial injury (AI), and AI with tadalafil treatment (AI-tadalafil) groups. AI and AI-tadalafil groups underwent endothelial injury of the iliac arteries and received a 2% cholesterol diet following AI. AI-tadalafil rats were treated with tadalafil (2 mg/kg/day) orally for 8 weeks after AI. The control group received a regular diet. After 8 weeks, animals were sacrificed, and pharmacological and morphological studies on prostate tissues were performed.

RESULTS

Iliac arteries from AI rats displayed neo-intimal formation and luminal occlusion, an effect that was not prevented by tadalafil treatment. In the AI group, there was an obvious epithelial atrophy and a statistically significant increase in collagen fibers compared with the controls. Immunohistochemically, there was an up-regulation of smooth muscle α-actin (SMA). Contractile responses of prostate strips to KCl, electrical field stimulation (EFS), and phenylephrine (PE) were significantly higher after AI than in controls. Chronic treatment with tadalafil prevented the increase in contractile responses in ischemic tissue, and decreased the collagen deposition compared with the AI group.

CONCLUSIONS

In this rat model, chronic pelvic ischemia caused distinct functional and morphological changes in the prostate. Prostatic tissue from ischemic animals showed an increased contractile response to electrical and pharmacological stimulation, an increase in SMA, and an increased deposition of collagen. All these changes could be prevented by treatment with the PDE5 inhibitor, tadalafil, suggesting an involvement of cyclic guanosine monophosphate (cGMP).

Comparison of the efficacy of isosorbide mononitrate and doxazosin in the treatment of lower urinary tract symptoms and benign prostatic hyperplasia: a randomized clinical trial

OBJECTIVE

We aimed to compare the efficacy of isosorbide mononitrate and doxazosin in the treatment of lower urinary tract symptoms (LUTS).

PATIENTS AND METHODS

80 patients with LUTS were included in this randomized clinical study. All patients were evaluated with uroflowmetry, post-void residual (PVR) urine, prostate volume, International Prostate Symptom Score (IPSS), serum PSA, urinalysis and culture. 40 patients were prescribed doxazosin for 4 weeks, another 40 were prescribed isosorbide mononitrate for 4 weeks. Urologic re-evaluation was done at the end of the study.

RESULTS

74 patients completed the study. The mean age of patients was 59.6 ± 0.7 years, the mean PSA value was 1.7 ± 0.1 ng/ml and the mean prostate volume was 41.9 ± 1.7 ml. Doxazosin markedly improved IPSS (from 16.2 ± 0.7 to 9.5 ± 0.5), maximum urinary flow rate (from 10.9 ± 0.7 to 12.8 ± 0.6 ml/s) and PVR urine (from 68.1 ± 9.4 to 39.0 ± 4.4 ml) (p < 0.0001, p < 0.0001, p = 0.0004, respectively). Isosorbide only improved IPSS (from 16.5 ± 0.9 to 14.6 ± 0.8) (p = 0.032).

CONCLUSIONS

Daily administration of isosorbide does not seem to be an alternative to α-blocker therapy. Controlled, randomized novel studies are required to establish that whether nitric oxide donors are an effective alternative in LUTS treatment.

Novel drug targets for the pharmacotherapy of benign prostatic hyperplasia (BPH)

Benign prostatic hyperplasia (BPH) is the major cause of lower urinary tract symptoms in men aged 50 or older. Symptoms are not normally life threatening, but often drastically affect the quality of life. The number of men seeking treatment for BPH is expected to grow in the next few years as a result of the ageing male population. Estimates of annual pharmaceutical sales of BPH therapies range from $US 3 to 10 billion, yet this market is dominated by two drug classes. Current drugs are only effective in treating mild to moderate symptoms, yet despite this, no emerging contenders appear to be on the horizon. This is remarkable given the increasing number of patients with severe symptoms who are required to undergo invasive and unpleasant surgery. This review provides a brief background on prostate function and the pathophysiology of BPH, followed by a brief description of BPH epidemiology, the burden it places on society, and the current surgical and pharmaceutical therapies. The recent literature on emerging contenders to current therapies and novel drug targets is then reviewed, focusing on drug targets which are able to relax prostatic smooth muscle in a similar way to the α(1) -adrenoceptor antagonists, as this appears to be the most effective mechanism of action. Other mechanisms which may be of benefit are also discussed. It is concluded that recent basic research has revealed a number of novel drug targets such as muscarinic receptor or P2X-purinoceptor antagonists, which have the potential to produce more effective and safer drug treatments.

Phosphodiesterase type 5 inhibitors in the management of non-neurogenic male lower urinary tract symptoms: critical analysis of current evidence

CONTEXT

A large body of epidemiologic data suggests a causal relationship between lower urinary tract symptoms (LUTS) and erectile dysfunction (ED). Recently reported studies on phosphodiesterase type 5 inhibitors (PDE5-Is) and LUTS have further contributed to the understanding of mechanisms involved in this relationship and of potential treatment options.

OBJECTIVE

A nonsystematic descriptive review was performed to summarize the literature concerning the role of PDE5-Is in men with LUTS, particularly looking at data derived from clinical trials in relation to the different PDE5-Is or their association with α-blockers.

EVIDENCE ACQUISITION

A comprehensive electronic search was conducted in October 2010 using the Medline database to identify all publications relating to ED and BPH and treatment with sildenafil, vardenafil, tadalafil, udenafil, UK-369003, and combination therapy with alfuzosin and tamsulosin.

EVIDENCE SYNTHESIS

In studies in which either ED or LUTS was the entry criterion, sildenafil appears to improve both erectile function and LUTS in subjects with ED. Placebo-controlled trials of tadalafil and vardenafil showed improvement of LUTS secondary to benign prostatic hyperplasia (BPH), but none of the studies showed a significant effect on urodynamic measures. Exploratory studies with UK-369003 showed improvements in LUTS and ED. Sildenafil or tadalafil associated with alfuzosin or tamsulosin showed greater benefits for the combination therapy for both LUTS and ED. The coadministration of udenafil and an α-blocker in patients with BPH and ED also appeared to improve both LUTS and ED severity.

CONCLUSIONS

Consistent evidence of improvements in LUTS has been shown with PDE5-Is, either alone or in combination with α-blockers. However, effects on urodynamics or objective measures of urinary flow are lacking. Further areas of research include investigation of mechanism of PDE5-Is, urodynamic studies, identification of new efficacy end points, head-to-head comparison with standard of care, potential benefit of add-on treatment, and long-term outcomes.

Tadalafil for the treatment of lower urinary tract symptoms secondary to benign prostatic hyperplasia: pathophysiology and mechanism(s) of action

BACKGROUND

The PDE5 inhibitor tadalafil is investigation for the treatment of lower urinary tract symptoms (LUTS) in men with benign prostatic hyperplasia (BPH). Several clinical studies of tadalafil and other PDE5 inhibitors have reported significant symptom reduction but limited urinary flow rate improvement. This manuscript reviews the published literature describing the pathophysiology of male LUTS, with an emphasis on mechanisms that may be modulated or improved by phosphodiesterase type 5 (PDE5) inhibition.

METHODS

Literature (through March 2010) was obtained via Medline searches and from the individual reviewers files. Articles were selected for review based on describing in vitro, preclinical, or clinical studies of pathological processes contributing to LUTS, or possible effects of PDE5 inhibition in the lower urinary tract.

RESULTS

Major mechanisms contributing to LUTS include: reduced nitric oxide/cyclic guanosine monophosphate signaling; increased RhoA kinase pathway activity; autonomic overactivity; increased bladder afferent activity; and pelvic ischemia. Tadalafil and other PDE5 inhibitors have demonstrated beneficial effects on smooth muscle relaxation, smooth muscle and endothelial cell proliferation, nerve activity, and tissue perfusion that may impact LUTS in men.

CONCLUSIONS

The pathophysiology of male LUTS is complex and not completely understood. LUTS may occur independently of BPH or secondary to BPH but in both cases involve obstructive or irritative mechanisms with substantial pathophysiological overlap. While the precise mechanism remains unclear, inhibition of PDE5 seems to have an effect on several pathways that may impact LUTS.

Is there a rationale for the chronic use of phosphodiesterase-5 inhibitors for lower urinary tract symptoms secondary to benign prostatic hyperplasia?

OBJECTIVES

To critically review the physiological roles of phosphodiesterase-5 (PDE5), to explain and support the putative impact and clinical significance of PDE5 inhibitors (PDE5-Is) in the treatment of lower urinary tract symptoms (LUTS) associated with benign prostatic hyperplasia (BPH) and erectile dysfunction (ED), both highly prevalent in men aged > or =50 years, as PDE5-Is are very effective as a first-line therapy for ED, and attractive for further physiological functional investigations.

METHODS

We searched Medline for peer-reviewed articles in English, from 1991 to 2008, to provide a critical contemporary review of PDE5 pertaining to the potential interest of findings supporting a role for PDE5-Is in LUTS due to BPH. The selection of papers was based on the relevance of subject matter. A critical analysis of available fundamental and clinical data is reported.

RESULTS

Several studies assessed the role of the nitric oxide/cGMP signalling pathway in the regulation of the prostate tone, with the support of clinical observations. PDE5-Is can also represent a potential mode of action allowing the targeting of transcriptional activity implicated in the regulation of the progression of the inflammatory process involved in BPH. PDE5-Is can inhibit human stromal cell proliferation of the prostate mediated by cGMP accumulation. New targeting hypotheses of pathophysiological processes are also reported.

CONCLUSIONS

There is evidence that LUTS and ED are strongly linked. This analysis of the regulatory basis of PDE5 biology could indicate several directions of investigation. However, it is necessary to devise well-designed large prospective studies that would produce significant data before this approach becomes a standard of care.

The relationship between erectile dysfunction and lower urinary tract symptoms and the role of phosphodiesterase type 5 inhibitors

CONTEXT

The relationship between lower urinary tract symptoms (LUTS) and erectile dysfunction (ED) and the potential interplay of phosphodiesterase type 5 inhibitors (PDE5-I) have clinical implications for both patient screening and treatment.

OBJECTIVE

To describe the current literature assessing the LUTS-ED relationship and the role of PDE5-I from both a basic science and clinical intervention perspective.

EVIDENCE ACQUISITION

We focused on data recently published (1990-2008) describing epidemiologic and mechanistic manuscripts of the LUTS-ED relationship with emphasis on papers involving PDE5-I-particularly those using level 1 evidence clinical trials. Base key words used included BPH, LUTS, ED, and phosphodiesterase inhibitors in combination with such secondary key words as nitric oxide, autonomic hyperactivity, Rho-kinase, atherosclerosis, and mechanism. We abstracted >200 articles and reviewed >100.

EVIDENCE SYNTHESIS

The large overlap of elderly men with both LUTS and ED likely stems from a cause-and-effect relationship. Thus far, four proposed mechanisms attempt to explain the relationship between LUTS and ED. Multiple studies showing that PDE5-I improved LUTS have been performed. Understanding the role of PDE5-I in the LUTS and ED relationship affects patient screening and treatment but also raises further research questions.

CONCLUSIONS

The future use of phosphodiesterase inhibitors as either prophylaxis or as a primary treatment for LUTS looms as a possibility and may not be limited to men.

The nitric oxide pathway in the human prostate: clinical implications in men with lower urinary tract symptoms

To date, there is an increasing interest in the nitric oxide (NO) pathway as a potential pharmacological target to treat male lower urinary tract symptomatology (LUTS). In the transition zone of the human prostate, a dense nitrinergic innervation has been shown of the fibromuscular stroma, glandular epithelium and blood vessels. The expression of key proteins of the NO pathway, such as the endothelial and neuronal nitric oxide synthase (eNOS, nNOS), cGMP-degrading phosphodiesterase type 5 (PDE5) and cGMP-binding protein kinase (cGK), has also been demonstrated. The hypothesis that an impaired NO/cGMP-signaling may contribute to the pathophysiology of benign prostatic hyperplasia (BPH) is supported by the results from randomized, placebo-controlled clinical studies, indicating that NO donor drugs and PDE5-inhibitors sildenafil, tadalafil and vardenafil may be useful to treat storage and voiding dysfunctions resulting from LUTS in men. Thus, given a potential role of the NO-pathway in the prostate and/or in other parts of lower urinary tract (e.g. bladder), the enhancement of the NO signaling by NO donor drugs, PDE5 inhibitors or activators of the soluble guanylyl cyclase (sGC) may represent a new therapeutic strategy for the treatment of LUTS. This review serves to focus on the role of NO and the NO-dependent signaling in the control of smooth muscle function in the human prostate. Results from clinical trials in men with LUTS/BPH are also discussed.

Phosphodiesterases (PDEs) and PDE inhibitors for treatment of LUTS

Lower urinary tract (LUT) smooth muscle can be relaxed by drugs that increase intracellular concentrations of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). Both of these substances are degraded by phosphodiesterases (PDEs), which play a central role in the regulation of smooth muscle tone. The distribution and functional significance of PDE enzymes vary in different tissues of the LUT. Targeting specific PDE isoenzymes should thus allow organ selectivity. PDE 4 and 5 appear to predominate in the prostate, PDE 1 and 4 are thought to influence detrusor smooth muscle function, and PDE 5 may be functionally important in the urethra and vasculature. Studies on the use of PDE inhibitors to treat various LUT symptoms (LUTS), have yielded favorable results. Thus, positive effects of the PDE 5 inhibitors sildenafil and tadalafil on symptoms and quality of life in men with LUTS, erectile dysfunction, and BPH have also been demonstrated. These effects may be due to effects on cGMP signaling and/or modification of afferent input from bladder, urethral, and prostate tissue. This review gives an update on the distribution of PDEs in structures relevant for LUT function, and discusses how inhibition of these enzymes can contribute to beneficial effects on LUTS. Information for the review was obtained from searches of the PubMed database, and from the authors' files.

Correlation between risk factors for vascular disease and the American Urological Association Symptom Score

OBJECTIVE

To evaluate the correlation between risk factors for vascular disease and the American Urological Association Symptom Score (AUA-SS), by comparing the presence of these risk factors with the degree of lower urinary tract symptoms (LUTS).

PATIENTS AND METHODS

We retrospectively reviewed the medical history, AUA-SS, and prostate volume of men who had a radical prostatectomy. The degree of LUTS in men with and without risk factors for cardiovascular disease was compared.

RESULTS

The mean AUA-SS was 7.2 for the entire cohort, 5.6 in men with no risk factors, and 7.9 in men with at least one risk factor (P < 0.05). In men with one to four risk factors, the mean AUA-SS was 6.9, 7.9, 10.7, and 19.5, respectively. There was no correlation between the AUA-SS and prostate size in the entire cohort or among any groups.

CONCLUSIONS

Men with risk factors for vascular disease are more likely to have a higher AUA-SS than men without these risk factors. These findings suggest the possibility of an association between vascular disease and the development and severity of LUTS in men.

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.

Evaluation of short term clinical effects and presumptive mechanism of botulinum toxin type A as a treatment modality of benign prostatic hyperplasia

The purpose of this study was to evaluate the effect and investigate the putative mechanism of botulinum toxin type A (BTA) applied to the treatment of benign prostatic hyperplasia (BPH). A total of 52 patients with symptomatic BPH were evaluated. Transperineal intraprostatic injection under transrectal ultrasonography was carried out. BTA dissolved in 4 to 9 mL of saline was used from 100 U to 300 U, according to prostate volume. Twenty-six patients received only BTA (BT group), and 26 received both BTA and one month of an alpha-adrenergic antagonist (BTalpha group). The therapeutic outcomes were evaluated by comparing parameters such as international prostate symptom score (IPSS), quality of life, prostate specific antigen, prostate volume, post-void residual urine, and peak urinary flow rate. At the one month follow- up, 18 patients in the BT group and 21 in the BTalpha group had subjective symptomatic relief (p = 0.337). Only IPSS5 (weak stream) was significantly different between the BT group and BTalpha groups (p = 0.034). At the three month follow-up, 39 patients had subjective symptomatic relief. The storage symptoms were improved more than the voiding symptoms. Additionally, about 50 percent of the patients whose voiding symptom improved expressed improved erectile function. BTA injection seems to be an alternative treatment for BPH. The differences after the one month evaluation between the BT and the BTalpha groups might suggest that the adrenergic influence could be relatively reinforced by the anticholinergic effect of BTA. Nitric oxide would thus be involved in a BTA action mechanism in BPH.

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.

Spontaneous electrical activity in the prostate gland

The cellular mechanisms that underlie the initiation, maintenance and propagation of electrical activity in the prostate gland remain little understood. Intracellular microelectrode recordings have identified at least two distinct electrical waveforms: pacemaker potentials and slow wave activity. By analogy with the intestine, we have proposed that pacemaker activity arises from a morphologically distinct group of c-Kit positive interstitial cells that lie mainly between the glandular epithelium and smooth muscle layers. We speculate that pacemaker activity arising from the prostatic interstitial cells (PICs) is likely to propagate and initiate slow wave activity in the smooth muscle cells resulting in contraction of the stromal smooth muscle wall. While spontaneous electrical activity in the prostate gland is myogenic in origin, it is clear that nerve-mediated agents are able to modulate this activity. Excitatory agents such as histamine, phenylephrine and a raised potassium saline all increase slow wave discharge. In contrast, nitric oxide donors reduce or abolish the spontaneous electrical events. However, the cellular mechanisms underlying the action of various endogenously released agents remain to be elucidated.

In vitro functional responses of isolated normal human prostatic tissue to compounds interacting with the cyclic guanosine monophosphate pathway

OBJECTIVES

To examine the effects of some nitric oxide-donating agents, as well as the C-type natriuretic peptide (CNP), on isolated human prostatic tissue. To date, guanylyl cyclases and cyclic guanosine monophosphate (cGMP)-degrading phosphodiesterases represent important target proteins for the development of new drugs for the treatment of lower urinary tract symptoms and benign prostatic hyperplasia.

METHODS

Using the organ bath technique, the effects of sodium nitroprusside, S-nitrosoglutathione, S-nitrosocysteine, linsidomine, and CNP (1 nM to 1.0/10 microM) on the tension induced by norepinephrine of prostatic tissue strips were investigated. The tissue was also exposed to three different concentrations of the drugs, and the production of cGMP and cyclic adenosine monophosphate (cAMP) was determined.

RESULTS

The tension induced by 40 microM norepinephrine of the isolated prostatic tissue was dose dependently reversed by the drugs. The rank order of potency was sodium nitroprusside more than S-nitrosoglutathione more than linsidomine more than S-nitrosocysteine, which was equal to CNP (1 microM). The reversal of tension induced by the greatest drug concentrations ranged from 50% relaxation with sodium nitroprusside to 42% relaxation with CNP. The relaxing effects of the drugs were paralleled by a 2-fold to 40-fold and 2-fold to 45-fold increase in tissue levels of cAMP and cGMP, respectively.

CONCLUSIONS

Our results provide further evidence that cGMP and cAMP are involved in the control of the normal function of human prostatic smooth muscle. Our findings may provide new strategies for future therapeutics used in the treatment of lower urinary tract symptoms and bladder outlet obstruction secondary to benign prostatic hyperplasia.

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.

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.

Effect of periurethral denervation on function of the female urethra

OBJECTIVE

The purpose of this study was to determine the effect of periurethral denervation on contractile function of the female rat urethra.

STUDY DESIGN

Periurethral nerve transection or sham operation was performed in 16 young female rats. After 2 weeks, contractile function of the external urethra sphincter (EUS) and longitudinal smooth muscle was determined. Inhibitors of nitric oxide (NO) signaling were used to evaluate the role of nitric oxide in nerve-mediated relaxation. Statistical comparisons were conducted by Student t test.

RESULTS

Periurethral nerve transection resulted in gross evidence of urinary retention and bladder distention. In normal and sham-operated rats, nerve-mediated relaxation of urethral smooth muscle was inhibited by L-nitroarginine and oxadiazolo quinoxalin-1-one (ODQ), and this relaxation response was impaired significantly after periurethral nerve injury. Relaxation responses to the NO donor sodium nitroprusside remained intact. Contractile function of the EUS was not altered by periurethral nerve injury.

CONCLUSION

Neurons surrounding the urethra contain NO and innervate smooth muscle of the inner urethra. Periurethral denervation results in impaired urethral smooth muscle relaxation with no appreciable effect on contractility of the external striated sphincter.

Endothelial nitric oxide synthase gene polymorphisms and the shedding of circulating tumour cells in the blood of prostate cancer patients

The involvement of endothelial nitric oxide synthase (ecNOS) gene polymorphisms (ecNOS4a/b and Glu-Asp298) on the shedding of tumor cells in the blood of 61 patients with prostate cancer (PCa), was analyzed. Hematogenous micrometastasis with blood circulating tumor cells (CTCs) may be an early event in the natural history of PCa metastization. CTCs can be detected by the presence of messenger RNA prostate specific membrane antigen by reverse transcription-polymerase chain reaction. We found an association between ecNOS4a/b genotypes presenting the a allele (ab/aa) with the presence of CTCs in the blood of PCa under the age of 67 years (P=0.003) and with localized disease (P=0.012). This association was not found for Glu-Asp298 genotypes. In summary, we have identified a nitric oxide related genetic factor associated with micrometastization of prostate cancer. We hypothesize that genotypes with the a allele of the ecNOS4a/b polymorphism may facilitate the survival of CTCs in the blood of cancer patients.

Common conditions of the aging male: erectile dysfunction, benign prostatic hyperplasia, cardiovascular disease and depression

With increasing life expectancy, medical profession will be faced with the task of ensuring that the large, aging population remains healthy and vital despite the face of increasing healthcare costs. Naturally, urology as a specialty is concerned with important geriatric issues. This article will focus specifically on the aging male population and the health problems that most frequently plague them. Four major, non-cancer, disease states have been identified that adversely effect males over the age of 50. These conditions are: erectile dysfunction (ED), benign prostatic hyperplasia (BPH), cardiovascular disease (CVD) and depression. A literature search of PubMed was conducted using the key words ED, BPH, CVD and depression as well as ADAM (Androgen Decline in the Aging Male) and quality of life (QoL). NIH and WHO conference proceedings and publications were also referenced to insure detail and accuracy of data. Information was then organized and correlated in order to provide a detailed description of the key conditions and their interrelatedness. The spectrum of research performed thus far regarding this topic has done little to investigate the effects, causes and correlations between these conditions. Research has been done linking two or three of these conditions; however, there remains to be information discussing the four disease states in terms of their possible cause and effect relationships or the effectiveness of parallel, multi-disciplinary approach to their therapy. This report calls attention to the benefits of viewing and researching the above mentioned conditions as possibly interrelated, as opposed to the traditional view of them as separate, unrelated and independently treatable disease states. ED, BPH, CVD and depression are all common conditions that accompany aging and negatively impact QoL. They almost always develop with age and precipitate considerable morbidity and may even result in mortality. Furthermore, the presentation of one condition may correlate with the development of another. The inter-relation of these conditions, as evident from their underlying similarities, cause-and-effects relationships and therapeutic consequences, should be enough to warrant a multidisciplinary approach to their research. This approach, combined with careful choice of therapy, parallel and singular, will help providers reach their goal to keep patients healthy, and more importantly happy, late into their life, thus realizing the concept of "successful aging".

Endothelial nitric oxide synthase gene polymorphisms and genetic susceptibility to prostate cancer

The endothelial cell-specific form of nitric oxide synthases (ecNOS) is localized at 7q35-q36 and is involved in vascular development and tumour growth in human prostate cancer. We have conducted a case-control study to investigate the prevalence of two polymorphisms at intron 4 (ecNOS4a/b) and exon 7 (Glu-Asp298) of ecNOS gene in 125 prostate cancer (PCa) patients and in 153 controls. We observed that the a-allele (aa or ab genotypes from ecNOS4a/b) was over-presented in the group of PCa with Gleason histological grade >or=7 (P=0.041). With regard to the Glu-Asp298 polymorphism, patients with the T-allele were younger than patients with no T-allele (P=0.037), and a statistically significant difference was noted in the Glu-Asp298 genotype distribution between cases with advanced disease and cases with localized disease (P=0.0013). When comparing cases and controls with logistic regression analysis we observed that the presence of the a-allele is associated with prostate cancer risk (odds ratio (OR) 1.83; 95% confidence interval (CI) 1.06-3.17; P=0.029), to high histological grade (Gleason >or=7) of PCa (OR 2.18; 95% CI 0.95-4.98; P=0.062) and with the risk of progression of the cancer disease (OR 2.85; 95% CI 1.19-6.82; P=0.018). Furthermore, we found that carriers with the combination of the a-allele (aa and ab ecNOS4a/b genotypes) and T-allele (GT and TT from Glu-Asp298) have a threefold increase in prostate cancer risk (OR 3.13; 95% CI 1.41-6.91, P=0.004). In summary, we have identified an NO-related genetic risk factor for prostate cancer that may help in understanding the molecular mechanism involved in the individual susceptibility to prostate cancer.

Cholinergic innervation and function in the prostate gland

The mammalian prostate is densely innervated by hypogastric and pelvic nerves that play an important role in regulating the growth and function of the gland. While there has been much interest in the role of the noradrenergic innervation and adrenoceptors in prostate function, the role of cholinergic neurones in prostate physiology and pathophysiology is not well understood. This review focuses on the role of acetylcholine and cholinoceptors in prostate function. Nitric oxide, vasoactive intestinal polypeptide, and/or neuropeptide Y are co-localised with cholinesterase and/or acetylcholine transporter in some of the nerve fibres supplying the prostate. Their roles are also briefly discussed in this review. A dense network of cholinesterase-staining fibres supplies both prostate epithelium and stroma, suggesting a role of acetylcholine and/or co-localised neuropeptides in the modulation of prostatic secretions, as well as smooth muscle tone. A predominantly epithelial location for prostate muscarinic receptors indicated a major secretomotor role for acetylcholine. The muscarinic receptor subtype mediating muscarinic agonist-induced smooth muscle contraction or enhancement of contractions evoked by nerve stimulation differs in different species. In the human, there is evidence for M(1) receptors on the epithelium, M(2) receptors on the stroma, and both M(1) and M(3) receptors in some prostate cancer cell lines. Several recent investigations indicate that muscarinic receptors may also mediate or modulate normal, benign, and malignant prostate growth. The role of muscarinic agonists and their receptors and the influences of age, testicular, and other steroids in regulating the effects are reviewed.

Future concepts in the medical therapy of benign prostatic hyperplasia

The standard medical therapy for symptomatic benign prostatic hyperplasia is still alpha-blockers and 5alpha-reductase inhibitors. Ongoing studies demonstrate the long-term safety and efficacy of these two classes of therapeutic approaches. Although there have been no new Food and Drug Administration approved medical therapies for the treatment of benign prostatic hyperplasia over the past year, interest in and the use of phytotherapeutic agents continues to increase. In this review, we will discuss the developments that have occurred over the past year in the medical management of benign prostatic hyperplasia. In addition, we present ongoing efforts at our center to obtain a better understanding of and manipulate the apoptotic pathway as it pertains to the pathophysiology of benign prostatic hyperplasia.