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

Efficacy and safety of PDE5 inhibitors in middle-aged and old patients with and without hypogonadism

PURPOSE

Although several reviews have evaluated the use of PDE5 inhibitors (PDE5i) for treating erectile dysfunction (ED), their specific use in middle-aged and old patients has not been fully evaluated. Given that elderly patients with ED often have a complex combination of systemic and sexual health risk factors, the safety and efficacy of PDE5i in such a context are hereby reviewed.

MATERIALS AND METHODS

A thorough examination of existing literature has been conducted on PubMed.

RESULTS

PDE5i has good safety and efficacy, but the situation is more complex for patients with hypogonadism than those with normal testosterone levels, with reduced responsiveness to PDE5i. In this case, combination therapy with testosterone is recommended, safe and effective.

CONCLUSIONS

Eliminating or reducing reversible risk factors and controlling or slowing the development of irreversible factors is an important foundation for using PDE5i to treat ED in all patients, especially middle-aged and elderly ones.

A Review on the Pharmacological Importance of PDE5 and Its Inhibition to Manage Biomedical Conditions

Phosphodiesterase type 5 (PDE5) is a cyclic GMP (cGMP) specific protein. It hydrolyzes the phosphodiesterase linkage and catalyzes the conversion of cGMP to 5’ GMP, which controls different physiological activities of the body. PDE5 is associated with biomedical conditions like neurological disorders, pulmonary arterial hypertension, cardiomyopathy, cancer, erectile dysfunction, and lower urinary tract syndrome. Inhibition of PDE5 has now been proven pharmaceutically effective in a variety of therapeutic conditions. Avanafil, tadalafil, sildenafil, and vardenafil are the most commonly used PDE5 inhibitors (PDE5i) today which are often used for the management of erectile dysfunction, lower urinary tract syndromes, malignancy, and pulmonary arterial hypertension. However, these synthetic PDE5i come with a slew of negative effects. Some of the most common side effects include mild headaches, flushing, dyspepsia, altered color vision, back discomfort, priapism, melanoma, hypotension and dizziness, non-arteritic anterior ischemic optic neuropathy (NAION), and hearing loss. In light of the potential negative effects of this class of medications, there is a lot of room for new, selective PDE5 inhibitors to be discovered. We have found 25 plant botanical compounds effectively inhibiting PDE5 which might be useful in treating a variety of disorders with minimal or no adverse effects.

Phosphodiesterase 5 (PDE5): Structure-function regulation and therapeutic applications of inhibitors

Phosphodiesterase 5 (PDE5) is one of the most well-studied phosphodiesterases (PDEs) that specifically targets cGMP typically generated by nitric oxide (NO)-mediated activation of the soluble guanylyl cyclase. Given the crucial role of cGMP generated through the activation of this cellular signaling pathway in a variety of physiologically processes, pharmacological inhibition of PDE5 has been demonstrated to have several therapeutic applications including erectile dysfunction and pulmonary arterial hypertension. While they are designed to inhibit PDE5, the inhibitors show different affinities and specificities against all PDE subtypes. Additionally, they have been shown to induce allosteric structural changes in the protein. These are mostly attributed to their chemical structure and, therefore, binding interactions with PDE catalytic domains. Therefore, understanding how these inhibitors interact with PDE5 and the structural basis of their selectivity is critically important for the design of novel, highly selective PDE5 inhibitors. Here, we review the structure of PDE5, how its function is regulated, and discuss the clinically available inhibitors that target phosphodiesterase 5, aiming to better understand the structural bases of their affinity and specificity. We also discuss the therapeutic indications of these inhibitors and the potential of repurposing for a wider range of clinical applications.

Defining the Efficacy and Safety of Phosphodiesterase Type 5 Inhibitors with Tamsulosin for the Treatment of Lower Urinary Tract Symptoms Secondary to Benign Prostatic Hyperplasia with or without Erectile Dysfunction: A Network Meta-Analysis

Purpose

The purpose of this study was to compare the relative safety and efficacy of different types of phosphodiesterase type 5 inhibitors (PDE5-Is) with tamsulosin for the treatment of lower urinary tract symptoms (LUTS) secondary to benign prostate hyperplasia (BPH) (BPH-LUTS) with or without erectile dysfunction (ED).

Methods

We use the Stata version 13.0 to conduct the network meta-analysis (NMA) with a random effects model of the Bayesian framework. The International Prostate Symptom Score (IPSS), Maximum Urinary Flow Fate (Q_max), International Index of Erectile Function (IIEF), and their credible intervals (CI) were used to compare the efficacy and safety of every medical intervention, including sildenafil plus tamsulosin, tadalafil plus tamsulosin, and vardenafil plus tamsulosin.

Results

Seven RCTs including 531 participants with seven interventions were analyzed. The results of NMA SUCRA showed that compared with different doses or types of PDE5-Is combined with tamsulosin (0.4 mg qd), the sildenafil (25 mg qd) combined with tamsulosin (0.4 mg qd) group had the greatest probabilities of being the best in the achievement of improving IIEF. The sildenafil (25 mg 4 days per week) combined with tamsulosin (0.4 mg qd) group had the greatest probabilities of being the best in the achievement of improving Q_max, whereas sildenafil (25 mg qd) combined with tamsulosin (0.4 mg qd) ranked the best for the safety outcomes.

Conclusions

This meta-analysis indicates that sildenafil combined with tamsulosin is the best effective and tolerated treatment option for BPH-LUTS with or without ED. Further RCTs are strongly required to provide more direct evidence.

Phosphodiesterase inhibitors for lower urinary tract symptoms consistent with benign prostatic hyperplasia

BACKGROUND

Benign prostatic hyperplasia (BPH) refers to non-malignant enlargement of the prostate gland that may cause bothersome lower urinary tract symptoms (LUTS). Alpha-blockers (ABs) and 5-alpha reductase inhibitors (5-ARIs) are the mainstay of medical treatment. Recently, phosphodiesterase inhibitors (PDEIs) that so far have been used mainly to treat erectile dysfunction were introduced to treat male LUTS.

OBJECTIVES

To assess the effects of PDEIs compared to placebo and other standard of care drugs (ABs and 5-ARIs) in men with LUTS consistent with BPH.

SEARCH METHODS

We conducted a systematic search of the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, Web of Science, and clinical trials registries of the World Health Organization (WHO) and the National Institutes of Health (NIH) (updated 2 August 2018). We performed citation tracking and handsearching of abstracts and conference proceedings. We also contacted study authors to ask for additional information.

SELECTION CRITERIA

We considered for inclusion in this systematic review randomised controlled trials (RCTs) comparing PDEIs versus placebo, ABs, or 5-ARIs for at least four weeks in men with BPH-LUTS.

DATA COLLECTION AND ANALYSIS

Three review authors independently screened the literature and extracted data. Primary outcomes were effects on urinary symptoms as assessed by the International Prostate Symptom Score (IPSS-total; score ranging from 0 to 35, with higher values reflecting more symptoms), urinary bother as assessed by the Benign Prostatic Hyperplasia Impact Index (BPHII; score ranging from 0 to 13, with higher values reflecting more bother), and adverse events (AEs). We used GRADE to rate the quality of evidence. We considered short-term (up to 12 weeks) and long-term (12 weeks or longer) results separately.

MAIN RESULTS

We included a total of 16 randomised trials in this review. The results for primary outcomes are as follows.PDEI versus placebo: PDEIs may result in a small improvement in IPSS-total score (mean difference (MD) 1.89 lower, 95% confidence interval (CI) 2.27 lower to 1.50 lower; n = 4293; low-quality evidence) compared to placebo, and may reduce the BPHII score slightly (MD 0.52 lower, 95% CI 0.71 lower to 0.33 lower; n = 3646; low-quality evidence). Rates of AEs may be increased (risk ratio (RR) 1.42, 95% CI 1.21 to 1.67; n = 4386; low-quality evidence). This corresponds to 95 more AEs per 1000 participants (95% CI 47 more to 151 more per 1000). Study results were limited to a treatment duration of six to 12 weeks.PDEI versus AB: PDEIs and ABs probably provide similar improvement in IPSS-total score (MD 0.22 higher, 95% CI 0.49 lower to 0.93 higher; n = 933; moderate-quality evidence) and may have a similar effect on BPHII score (MD 0.03 higher, 95% CI 1.10 lower to 1.16 higher; n = 550; low-quality evidence) and AEs (RR 1.35, 95% CI 0.80 to 2.30; n = 936; low-quality evidence). This corresponds to 71 more AEs per 1000 participants (95% CI 41 fewer to 264 more per 1000). Study results were limited to a treatment duration of six to 12 weeks.PDEI and AB versus AB alone: the combination of PDEI and AB may provide a small improvement in IPSS-total score (MD 2.56 lower, 95% CI 3.92 lower to 1.19 lower; n = 193; low-quality evidence) compared to AB alone. We found no evidence for BPHII scores. AEs may be increased (RR 2.81, 95% CI 1.53 to 5.17; n = 194; moderate-quality evidence). This corresponds to 235 more AEs per 1000 participants (95% CI 69 more to 542 more per 1000). Study results were limited to treatment duration of four to 12 weeks.PDEI and AB versus PDEI alone: the combination of PDEI and AB may provide a small improvement in IPSS-total (MD 2.4 lower, 95% CI 6.47 lower to 1.67 higher; n = 40; low-quality evidence) compared to PDEI alone. We found no data on BPHII or AEs. Study results were limited to a treatment duration of four weeks.PDEI and 5-ARI versus 5-ARI alone: in the short term (up to 12 weeks), the combination of PDEI and 5-ARI probably results in a small improvement in IPSS-total score (MD 1.40 lower, 95% CI 2.24 lower to 0.56 lower; n = 695; moderate-quality evidence) compared to 5-ARI alone. We found no evidence on BPHII scores or AEs. In the long term (13 to 26 weeks), the combination of PDEI and 5-ARI likely results in a small reduction in IPSS-total score (MD 1.00 less, 95% CI 1.83 lower to 0.17 lower; n = 695; moderate-quality evidence). We found no evidence about effects on BPHII scores. There may be no difference in rates of AEs (RR 1.07, 95% CI 0.84 to 1.36; n = 695; low-quality evidence). This corresponds to 19 more AEs per 1000 participants (95% CI 43 fewer to 98 more per 1000).We found no trials comparing other combinations of treatments or comparing different PDEI agents.

AUTHORS' CONCLUSIONS

Compared to placebo, PDEI likely leads to a small reduction in IPSS-total and BPHII sores, with a possible increase in AEs. There may be no differences between PDEI and AB with regards to improvement in IPSS-total, BPHII, and incidence of AEs. There appears to be no added benefit of PDEI combined with AB compared to PDEI or AB alone or PDEI combined with 5-ARI compared to ARI alone with regards to urinary symptoms. Most evidence was limited to short-term treatment up to 12 weeks and of moderate or low certainty.

PDE5 inhibitors - pharmacology and clinical applications 20 years after sildenafil discovery

The discovery of the nitric oxide/cGMP pathway was the basis for our understanding of many normal physiological functions and the pathophysiology of several diseases. Since the discovery and introduction of sildenafil, inhibitors of PDE5 have been the first-line therapy for erectile dysfunction (ED). The success of sildenafil in the treatment of ED stimulated research in the field of PDE5 inhibition and led to many new applications, such as treatment of lower urinary symptoms, and pulmonary arterial hypertension, which are now approved indications. However, PDE5 inhibitors have also been used in several other disorders not discussed in this review, and the fields of clinical use are increasing. In the present review, the pharmacological basis of the NO/cGMP pathway and the rationale and clinical use of PDE5 inhibitors in different diseases are discussed.

Erectile Dysfunction and Associated Risk Factors in Chinese Males of Infertile Couples

BACKGROUND

Knowledge on the occurrence of erectile dysfunction (ED) and timely ovulatory intercourse failure (TOIF) in Chinese men of infertile couples is limited.

AIM

To obtain representative estimates of ED and TOIF in Chinese men of infertile couples and to analyze potential risk factors associated with ED.

METHODS

4,299 Chinese men of infertile couples with an average age of 32.85 ± 5.98 years were surveyed using the 5-item International Index of Erectile Function (IIEF-5) questionnaire for their ED occurrence. Multiple logistic regression analysis was used to disclose risk factors associated with ED.

OUTCOMES

The occurrence of ED was 57.8% and that of TOIF was up to 26.2% in Chinese men of infertile couples.

RESULTS

Based on IIEF-5 criteria, 34.9% of men had mild ED and only 2.6% had severe ED. Secondary infertility, infertility with known causes, and chronic prostatitis were significant risk factors associated with ED. TOIF was significantly higher (23.3%) in men of infertile couples with ED than in those without ED (8.6%), indicating that TOIF is likely a contributing factor to male infertility.

CLINICAL IMPLICATIONS

Understanding the occurrence and types of ED and TOIF in men of infertile couples and their associated risk factors will help physicians treat clinical cases of male infertility more effectively.

STRENGTHS AND LIMITATIONS

Large numbers of infertile outpatients from multiple hospital clinics across the country were included in this study. The concept of TOIF was raised for the 1st time and studied preliminarily in Chinese men of infertile couples. The lack of participants' psychological status, a control group of men of fertile couples, and measurement of testosterone levels was a limitation in this clinic-based study.

CONCLUSION

The occurrence of ED was higher in Chinese men of infertile couples than in the general Chinese male population. Yang B, Xu P, Shi Y, et al. Erectile Dysfunction and Associated Risk Factors in Chinese Males of Infertile Couples. J Sex Med 2018;15:671-677.

Sildenafil citrate in combination with tamsulosin versus tamsulosin monotherapy for management of male lower urinary tract symptoms due to benign prostatic hyperplasia: A randomised, double-blind, placebo-controlled trial

Objective

To assess the additive effect of sildenafil citrate to tamsulosin in the treatment of lower urinary tract symptoms due to benign prostatic hyperplasia (LUTS/BPH) in men with or without erectile dysfunction (ED).

Patients and methods

In all, 150 men with untreated LUTS/BPH with or without ED were randomised to receive sildenafil 25 mg once daily (OD) or placebo OD (night time) combined with tamsulosin 0.4 mg OD (day time) for 6 months. Changes from pre-treatment scores in International Prostate Symptom Score (IPSS), IPSS-quality of life (QoL) score, maximum urinary flow rate (Q_max), and the five-item version of the International Index of Erectile Function questionnaire (IIEF-5) were assessed at 3 and 6 months. Safety profiles were assessed by physical examination and monitoring clinical adverse events.

Results

Group A comprised of men who received tamsulosin and sildenafil (75 men), whilst those in Group B received tamsulosin and placebo (75). The IPSS was significantly improved in Group A compared to Group B, at −29.3% vs −13.7% (P = 0.039) at 3 months and −37% vs −19.6% (P = 0.043) at 6 months after treatment. Q_max significantly improved in both groups compared with before treatment (P < 0.001). The IIEF-5 scores improved more in Group A than in Group B, at 58.7% vs 11.7% at 3 months and 62.4% vs 12.4% at 6 months after treatment (both P < 0.001).

Conclusion

Sildenafil citrate combined with tamsulosin improved LUTS, erectile function, and patient QoL more than tamsulosin monotherapy with the merit of a comparable safety profile in patients with LUTS/BPH.

Impact of postoperative phosphodiesterase type 5 inhibitor treatment on lower urinary tract symptoms after robot-assisted radical prostatectomy: a longitudinal study

OBJECTIVE

This study aimed to assess the role of tadalafil, a phosphodiesterase type 5 inhibitor (PDE5-I), in recovery of lower urinary tract symptoms (LUTS) after robot-assisted radical prostatectomy (RARP).

MATERIALS AND METHODS

All patients treated with RARP between October 2010 and August 2013 were enrolled in this retrospective study on prospectively collected data. Patients were retrospectively divided into groups according to postoperative treatment: patients taking tadalafil twice weekly from 1 month to 6 months after RARP, and patients not taking tadalafil. The International Prostate Symptom Score (IPSS), the Overactive Bladder Symptom Score (OABSS) and urinary continence (UC) were assessed preoperatively (2 days before RARP) and at 1, 3, 6, 9 and 12 months after RARP.

RESULTS

There was no difference in the overall IPSS score between the groups. At 6 and 9 months, the IPSS storage symptom scores were significantly lower in patients taking tadalafil than in patients not taking tadalafil. In patients with overactive bladder (OAB) before RARP (n = 22), no differences in the total scores of OABSS were seen between patients taking tadalafil and patients not taking tadalafil. On the other hand, in non-OAB patients before RARP (n = 68), at 3, 6 and 9 months, the total scores of OABSS were significantly lower in patients taking tadalafil than in patients not taking tadalafil. No differences in UC rates after surgery were seen between the groups.

CONCLUSION

Postoperative tadalafil treatment may be temporarily effective for the recovery of the IPSS storage symptom scores and OABSS.

Comparative Effectiveness of Newer Medications for Lower Urinary Tract Symptoms Attributed to Benign Prostatic Hyperplasia: A Systematic Review and Meta-analysis

CONTEXT

Alpha-blockers (ABs) and 5-alpha reductase inhibitors have an established role in treating male lower urinary tract symptoms (LUTS) attributed to benign prostatic hyperplasia (BPH). Recently, newer drugs have shown promise for this indication.

OBJECTIVE

To assess the comparative effectiveness and adverse effects (AEs) of newer drugs to treat LUTS attributed to BPH through a systematic review and meta-analysis.

EVIDENCE ACQUISITION

Ovid MEDLINE, the Cochrane Central Register of Controlled Trials, and Ovid Embase bibliographic databases (through June 2016) were hand searches for references of relevant studies. Eligible studies included randomized controlled trials published in English of newer ABs, antimuscarinics, a beta-3 adrenoceptor agonist, phosphodiesterase type-5 inhibitors, or combination therapy with one of these medications as an active comparator. Observational studies of the same agents with a duration ≥1 yr that reported AEs were also included.

EVIDENCE SYNTHESIS

We synthesized evidence from 43 randomized controlled trials as well as five observational studies. Based on improvement of mean International Prostate Symptom Score and quality of life scores, the effectiveness of the newer ABs was not different from the older ABs (moderate strength of evidence [SOE]), but had more AEs (low SOE). Antimuscarinics/AB combination therapy had similar outcomes as AB monotherapy (all moderate SOE), but often had more AEs. Phosphodiesterase type-5 inhibitors alone or in combination with ABs had similar or inferior outcomes than ABs alone. Evidence was insufficient for the beta-3 adrenoceptor agonist. For all newer agents, the evidence was generally insufficient to assess long-term efficacy, prevention of symptom progression, or AEs.

CONCLUSIONS

None of the drugs or drug combinations newly used to treat LUTS attributed to BPH showed outcomes superior to traditional AB treatment. Given the lack of superior outcomes, the studies' short time-horizon, and less assurance of their safety, their current value in treating LUTS attributable to BPH appears low.

PATIENT SUMMARY

In this paper, we reviewed the evidence of newer drugs to treat men with urinary problems attributable to an enlarged prostate. We found none of the new drugs to be better but there was more concern about side effects.

Review of the pathophysiological aspects involved in urological disease associated with metabolic syndrome

INTRODUCTION

Metabolic syndrome is a constellation of disorders that includes insulin resistance, central obesity, arterial hypertension and hyperlipidaemia. These disorders can have implications for the genitourinary apparatus.

OBJECTIVES

To conduct a review on the pathophysiological aspects that explain the relationship between metabolic syndrome and sexual dysfunction, lower urinary tract syndrome, prostate cancer and stone disease.

METHODS

We performed a qualitative, narrative literature review through a literature search on PubMed of articles published between 1997 and 2015, using the terms pathophysiology, metabolic syndrome, endothelial dysfunction, lipotoxicity, mitochondrial dysfunction, kidney stones, hypogonadism, erectile dysfunction, lower urinary tract syndrome and prostate cancer.

SYNTHESIS OF THE EVIDENCE

Metabolic syndrome constitutes an established complex of symptoms, defined as the presence of insulin resistance, central obesity, hypertension and hyperlipidaemia. Endothelial dysfunction secondary to lipotoxicity generates an inflammatory state, which involves renal cell metabolism, vascularisation of the pelvis and androgen production. These facts explain the relationship between metabolic syndrome, nephrolithiasis, lower urinary tract syndrome, hypogonadism and erectile dysfunction in men.

CONCLUSIONS

Strategies such as proper diet, regular exercise, insulin treatment, testosterone-replacement therapy, therapy with antioxidants and free-radical inhibitors and urological treatments classically used for lower urinary tract syndrome have shown promising results in this syndrome.

A Meta-Analysis of Long- Versus Short-Acting Phosphodiesterase 5 Inhibitors: Comparing Combination Use With α-Blockers and α-Blocker Monotherapy for Lower Urinary Tract Symptoms and Erectile Dysfunction

Purpose:

Combination therapy with an α-1-adrenergic blocker and phosphodiesterase type 5 inhibitors (PDE5Is) has shown improvements in lower urinary tract symptoms (LUTS) with negligible side effects. Nonetheless, decisive advantages in symptom improvement were insufficient, and there were no clinical differences between long- or short-acting PDE5Is in combination with combination medication.

Methods:

To review the studies on α-1-adrenergic blocker monotherapy and combination therapy with long vs. short-acting PDE5Is in their use in LUTS and erectile dysfunction (ED). A search of the MEDLINE, Embase, Cochrane Library, and KoreaMed databases was conducted from 2000 to 2014 using combinations of the relevant terms. Among the 323 relevant references discovered, 10 were selected for meta-analysis. The data showed that 616 men received combination therapy (PDE5Is with α-1-adrenergic blockers) or α-1-adrenergic blocker monotherapy.

Results:

Meta-analysis of the combination therapy showed it was more effective than α-blockers in improving symptoms, with a mean International Prostrate Symptom Score change difference of –1.93 while those of the long- vs. short-acting PDE5I were –2.12 vs. –1.70. Compared to maximum flow rate (Qmax) value with monotherapy, the Qmax increased more with the combination therapy (mean difference of 0.71) while change values were 0.14 and 1.13 for the long- and short-acting PDE5Is, respectively. Residual urine decreased more with the combination therapy than it did with α-1-adrenergic blocker monotherapy with a mean difference of –7.09 while the mean residual urine change values for long- vs. short-acting PDE5Is were –18.83 vs. –5.93. The International Index of Erectile Function value increased by 3.99, 2.85, and 4.85 following combination therapy, and therapy with long- and short-acting PDE5Is.

Conclusions:

Our meta-analysis suggests that PDE5Is can significantly improve LUTS in men with benign prostatic hyperplasia/ED. Furthermore, combination PDE5I and α-1-adrenergic blocker could be a more effective treatment than α-1-adrenergic blocker monotherapy, and the differences between long and short-acting agents were minimal.

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.

The role of phosphodiesterase-5 inhibitors in prostatic inflammation: a review

Clinical and basic experimental evidence indicates that chronic inflammation is the greatest factor in benign prostatic hyperplasia (BPH) progression, which is the most common cause of Lower Urinary Tract Symptoms (LUTS). The use of anti-inflammatory agents such as steroids, cyclooxygenase-2 (COX-2) and phytotherapics have been investigated as forms of treatment for various prostate diseases. Recent evidence has demonstrated that PDE5 inhibitors (PDE5Is) improve symptoms of BPH/LUTS, possibly as a result of the relaxing of the smooth muscle fibers of the bladder and prostate by NO/cGMPc signaling, or by improving RhoA/Rho-kinase (ROCK), and reduction of the hyperactivity of the autonomic nervous system. However, some results have suggested that besides vasodilatation and their anti-proliferative effect, PDE5Is exert a direct anti-inflammatory effect, by raising cGMP. Given that inflammation is major factor in benign prostatic hyperplasia (BPH) progression, PDE5Is could act also restore prostatic function as they act as potent anti-inflammatory drugs. This review aims to provide a comprehensive summary of the use of phosphodiesterase-5 inhibitors to treat prostatic inflammation.

Emerging drugs for overactive bladder

INTRODUCTION

Overactive bladder (OAB) is a common problem which can have disastrous effects on the quality of life of the sufferer. There are established treatments for the problem but they have significant adverse effects. Better drugs and new treatment modalities are necessary to deal with OAB.

AREA COVERED

Antimuscarinics, mirabegron and intravesical injection of botulinum toxin A are established treatments for OAB. Sacral neuromodulation is more invasive but has been successful in treating OAB. Phase II and III trials are in progress for newer β3-agonists and various combinations of antimuscarinics, β3-agonists and antidiuretics. Targeted secretion inhibitors (TSI) can increase efficacy and reduce adverse effects. Liposome integrated botulinum toxin A has an advantage of effective administration by intravesical instillation. Both medicines are in Phase II trials. Many other drugs which have promising results are discussed.

EXPERT OPINION

Newer antimuscarinics have better tolerability. Long-term data for mirabegron has shown that it is more effective in severe OAB. Combination drugs may prove to be more effective with less adverse effects. Emerging treatments with TSI, lipotoxin and gene therapy appear promising.

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).

Pharmacological treatment of chronic pelvic ischemia

Epidemiological studies have shown that lower urinary tract symptoms, including overactive bladder, commonly occur in both men and women, with an age-related increase in both sexes. Vascular endothelial dysfunction and urological symptoms are common in the metabolic syndrome; they also occur during the human ageing process and are independent risk factors for the development of atherosclerosis and hypertension. Pelvic arterial insufficiency may lead to impaired lower urinary tract perfusion and play an important role in the development of bladder dysfunction such as detrusor overactivity and overactive bladder. It seems reasonable, but has not been definitely established clinically, that chronic ischemia-related bladder dysfunction will progress to bladder underactivity. Studies in experimental models in rabbits and rats have shown that pelvic arterial insufficiency may result in significant bladder ischemia with reduced bladder wall oxygen tension, oxidative stress, increased muscarinic receptor activity, ultrastructural damage, and neurodegeneration. Several types of drug may be able to prevent some of these changes. Even if the α1-adrenoceptor blocker, silodosin, the phosphodiesterase type 5 inhibitor, tadalafil, the β3-α1-adrenoceptor agonist, mirabegron, and the free radical scavenger, melatonin, were unable to prevent the development of neointimal hyperplasia and consequent luminal occlusion in animal models, they all exerted a protecting effect on urodynamic parameters, and on the functional and morphological changes of the bladder demonstrable in vitro. The different mechanisms of action of the drugs suggest that many factors are involved in the pathogenesis of chronic ischemia-induced bladder dysfunction and can be targets for intervention. Since several of the agents tested are used clinically and effectively for relieving lower urinary tract symptoms, the results from animal models of chronic bladder ischemia seem to have translational value. Animal models may be of relevance for designing clinical studies to demonstrate if a certain drug may prevent progression of ischemia-related functional and morphological bladder changes.

Udenafil for the treatment of erectile dysfunction

Erectile dysfunction (ED) is often perceived by both patients and sexual partners as a serious problem that can jeopardize quality of life, psychosocial or emotional well-being, and the partnership in the long term. Since their introduction, oral phosphodiesterase type 5 inhibitors (PDE5Is) have been found to be highly effective and well tolerated, and are available as the first-line therapy for the treatment of ED. Udenafil is one of the selective PDE5Is made available in recent years for the treatment of ED. Udenafil has clinical properties of both relatively rapid onset and long duration of action due to its pharmacokinetic profile, thereby providing an additional treatment option for ED men to better suit individual needs. There is positive evidence that udenafil is effective and well tolerated in the treatment of ED of a broad spectrum of etiologies or severity. Udenafil is as effective in the treatment of diabetes mellitus-associated ED as other PDE5Is. Due to the clinical property of relatively long duration of action, udenafil may be another option in daily dosing treatment for ED, as suggested by its favorable efficacy and safety profile. Most adverse effects reported from clinical trials are mild or moderate in severity, without any serious adverse event, with headache and flushing being the most common. Also, the concomitant use of anti-hypertensive drugs or alpha-1-blockers does not significantly affect the efficacy and safety profile of udenafil. However, additional studies with larger cohorts including prospective, multicenter, comparative studies with patients of different ethnicities are needed to further validate the favorable findings of udenafil in the treatment of ED.

[Medicinal therapy of benign prostate syndrome with phosphodiesterase-5 inhibitors]

Phosphodiesterase-5 (PDE5) inhibitors, such as sildenafil, tadalafil and vardenafil are first line treatment for erectile dysfunction (ED). These PDE5 inhibitors are known to increase cyclic guanosine monophosphate (cGMP) concentrations in the smooth muscle cells of the corpora cavernosa penis by inhibiting PDE5, leading to smooth muscle relaxation. This mode of action is also believed to result in prostatic smooth muscle relaxation and to improve lower urinary tract symptoms (LUTS). Randomized controlled trials have shown beneficial effects on LUTS and on objective parameters such as maximum urinary flow rate (tadalafil). Based on these data tadalafil was recently approved for treatment of patients with male LUTS; however, the mechanisms leading to improvement of symptoms are still under debate.

Pathogenic mechanisms linking benign prostatic hyperplasia, lower urinary tract symptoms and erectile dysfunction

INTRODUCTION

Erectile dysfunction (ED) and lower urinary tract symptoms (LUTS) caused by benign prostatic hyperplasia (BPH) are clinical entities very prevalent in men aged over 50 years. There is evidence that both may have a common pathophysiology.

OBJECTIVE

The objective of this study was to conduct a literature review aiming to show theories and hypotheses that justify a single pathophysiology for ED and LUTS/BPH.

METHODS

A search in Medline using the keywords of the Medical Subject Headings (MESH) 'erectile dysfunction' and 'lower urinary tract symptoms' in all fields of the database up to 15 December 2012. This search found 198 relevant articles that were analyzed.

RESULTS

The data and articles were divided according to the type of evidence found. There are strong epidemiological data showing that LUTS/BPH is a risk factor for developing ED. Several experimental models demonstrated partial obstruction of the bladder in animals causes voiding disorders as well as a negative impact on erectile function of the operated animals. The increased adrenergic tonus in animals leads to prostate growth and urodynamic conditions similar to those found in men with LUTS and ED. Arteriosclerosis may lead to loss of vesical complacency, urinary tract obstruction and fibrosis of the cavernous bodies. The use of phosphodiesterase type 5 inhibitors (PDE-5i) and/or alpha-adrenergic blockers to treat ED and LUTS/BPH reinforces the hypothesis that, at least in some patients, both clinical pictures may have the same pathophysiology.

New therapies in the treatment of overactive bladder

INTRODUCTION

Overactive bladder (OAB) is a common condition which affects both men and women across many age groups with significant impact on quality of life. There is currently an armamentarium of treatment options available ranging from conservative, medical therapy to radical surgeries. Increasing understanding of OAB is resulting in the rapid development of new therapies today.

AREAS COVERED

The purpose of this article was to summarise the latest developments in non-neurogenic OAB treatment, discuss the evidence and results of current and new treatment modalities available through review of published data and results presented at recent international meetings.

EXPERT OPINION

The ultimate goal in OAB therapy is to provide good clinical efficacy, safe, non-invasive and easy to administer. There is definitely room for development of new therapies in OAB and current progress is encouraging.

Future direction in pharmacotherapy for non-neurogenic male lower urinary tract symptoms

BACKGROUND

The pathophysiology of male lower urinary tract symptoms (LUTS) is highly complex and multifactorial. The shift in perception that LUTS are not sex or organ specific has not been followed by significant innovations regarding the available drug classes.

OBJECTIVE

To review pathophysiologic mechanisms and clinical and experimental data related to the development of new pharmacologic treatments for male LUTS.

EVIDENCE ACQUISITION

The PubMed database was used to identify articles describing experimental and clinical studies of pathophysiologic mechanisms contributing to male LUTS and, supported by them, new pharmacotherapies with clinical or experimental evidence in the field.

EVIDENCE SYNTHESIS

Several pathologic processes (eg, androgen signaling, inflammation, and metabolic factors) and targets (eg, the urothelium, prostate, interstitial cells, detrusor, neurotransmitters, neuromodulators, and receptors) have been implicated in male LUTS. Some newly introduced drugs, such as phosphodiesterase type 5 inhibitors and β3-adrenergic agonists, have just started broad use in clinical practice. Drugs with potential benefit, such as vitamin D3 receptor analogs, gonadotropin-releasing hormone antagonists, cannabinoids, and drugs injected into the prostate, have been evaluated in experimental studies and have progressed to clinical trials. However, safety and efficacy data for these drugs are still scarce. Some compounds with interesting profiles have only been tested in experimental settings (eg, transient receptor potential channel blockers, Rho-kinase inhibitors, purinergic receptor blockers, and endothelin-converting enzyme inhibitors).

CONCLUSIONS

New pathophysiologic mechanisms of male LUTS are described that lead to the continuous development of new pharmacotherapies. To date, few drugs have been added to the current armamentarium, and several are in various phases of clinical or experimental investigation.

The use of a single daily dose of tadalafil to treat signs and symptoms of benign prostatic hyperplasia and erectile dysfunction

A strong and independent association between lower urinary tract symptoms suggestive of benign prostatic hyperplasia (LUTS/BPH) and erectile dysfunction (ED) has been widely evidenced in several clinical epidemiologic studies. Preclinical animal models have provided a great deal of information on potential common pathogenic mechanisms underlying these two clinical identities. Although the efficacy of the most commonly used treatments for LUTS/BPH is well defined, the negative impact of these treatments on sexual function – in particular, on ED – has triggered the search for new treatment options. In this regard, a new role for phosphodiesterase type 5 inhibitors in the treatment of LUTS/BPH and ED has been claimed. Tadalafil is one of the most extensively investigated phosphodiesterase type 5 inhibitors for this new indication. All evidence reported to date suggests that tadalafil 5 mg once daily is a safe and effective treatment option for both LUTS/BPH and ED.

Thermodynamic protonation constants of vardenafil by the nonlinear regression of multiwavelength pH-spectrophotometric titration data

pH-spectrophotometric titration data were used to determine protonation constants of vardenafil at different ionic strengths I and temperatures of 25°C and 37°C. The use of two different multiwavelength and the multivariate treatment of spectral data, SPECFIT32 and SQUAD(84) nonlinear regression analyses and INDICES factor analysis is presented. The reliability of the protonation constants of the drug was proven with goodness-of-fit tests of the pH-spectra. The thermodynamic protonation constants log K Ti were estimated by a nonlinear regression of (log K, I) data using the Debye-Hückel equation, yielding log K 4T = 3.59(1) and 3.26(1), log K 3T = 5.64(1) and 5.81(1), log K 2T = 9.41(1) and 8.59(2), log K 1T = 10.92(2) and 10.05(1) at 25°C and 37°C, where the figure in brackets is the standard deviation in last significant digit. Concurrently, the experimental determination of four thermodynamic protonation constants was combined with the computational prediction of the MARVIN program based on knowledge of the chemical structures of the drug and was in good agreement with its experimental value. The factor analysis of spectra in the INDICES program predicts the correct number of light-absorbing components when the instrument error is known and when the signal-to-error ratio SER is higher than 10.

Common theme for drugs effective in overactive bladder treatment: inhibition of afferent signaling from the bladder

The overactive bladder syndrome and detrusor overactivity are conditions that can have major effects on quality of life and social functioning. Antimuscarinic drugs are still first-line treatment. These drugs often have good initial response rates, but adverse effects and decreasing efficacy cause long-term compliance problems, and alternatives are needed. The recognition of the functional contribution of the urothelium/suburothelium, the autonomous detrusor muscle activity during bladder filling and the diversity of nerve transmitters involved has sparked interest in both peripheral and central modulation of overactive bladder syndrome/detrusor overactivity pathophysiology. Three drugs recently approved for treatment of overactive bladder syndrome/detrusor overactivity (mirabegron, tadalafil and onabotulinum toxin A), representing different pharmacological mechanisms; that is, β-adrenoceptor agonism, phosphodiesterase type 5 inhibition, and inhibition of nerve release of efferent and afferent transmitters, all seem to have one effect in common: inhibition of the afferent nervous activity generated by the bladder during filling. In the present review, the different mechanisms forming the pharmacological basis for the use of these drugs are discussed.

Phosphodiesterase type 5 inhibition reverts prostate fibroblast-to-myofibroblast trans-differentiation

Phosphodiesterase type 5 (PDE5) inhibitors have been demonstrated to improve lower urinary tract symptoms secondary to benign prostatic hyperplasia (BPH). Because BPH is primarily driven by fibroblast-to-myofibroblast trans-differentiation, this study aimed to evaluate the potential of the PDE5 inhibitor vardenafil to inhibit and reverse trans-differentiation of primary human prostatic stromal cells (PrSC). Vardenafil, sodium nitroprusside, lentiviral-delivered short hairpin RNA-mediated PDE5 knockdown, sodium orthovanadate, and inhibitors of MAPK kinase, protein kinase G, Ras homolog family member (Rho) A, RhoA/Rho kinase, phosphatidylinositol 3 kinase and protein kinase B (AKT) were applied to PrSC treated with basic fibroblast growth factor (fibroblasts) or TGFβ1 (myofibroblasts) in vitro, in chicken chorioallantoic membrane xenografts in vivo, and to prostatic organoids ex vivo. Fibroblast-to-myofibroblast trans-differentiation was monitored by smooth muscle cell actin and IGF binding protein 3 mRNA and protein levels. Vardenafil significantly attenuated TGFβ1-induced PrSC trans-differentiation in vitro and in chorioallantoic membrane xenografts. Enhancement of nitric oxide/cyclic guanosine monophosphate signaling by vardenafil, sodium nitroprusside, or PDE5 knockdown reduced smooth muscle cell actin and IGF binding protein 3 mRNA and protein levels and restored fibroblast-like morphology in trans-differentiated myofibroblast. This reversal of trans-differentiation was not affected by MAPK kinase, protein kinase G, RhoA, or RhoA/Rho kinase inhibition, but vardenafil attenuated phospho-AKT levels in myofibroblasts. Consistently, phosphatidylinositol 3 kinase or AKT inhibition induced reversal of trans-differentiation, whereas the tyrosine phosphatase inhibitor sodium orthovanadate abrogated the effect of vardenafil. Treatment of prostatic organoids with vardenafil ex vivo reduced expression of myofibroblast markers, indicating reverse remodeling of stroma towards a desired higher fibroblast/myofibroblast ratio. Thus, enhancement of the nitric oxide/cyclic guanosine monophosphate signaling pathway by vardenafil attenuates and reverts fibroblast-to-myofibroblast trans-differentiation, hypothesizing that BPH patients might benefit from long-term therapy with PDE5 inhibitors.

Therapeutic targeting of redox signaling in myofibroblast differentiation and age-related fibrotic disease

Myofibroblast activation plays a central role during normal wound healing. Whereas insufficient myofibroblast activation impairs wound healing, excessive myofibroblast activation promotes fibrosis in diverse tissues (including benign prostatic hyperplasia, BPH) leading to organ dysfunction and also promotes a stromal response that supports tumor progression. The incidence of impaired wound healing, tissue fibrosis, BPH, and certain cancers strongly increases with age. This paper summarizes findings from in vitro fibroblast-to-myofibroblast differentiation systems that serve as cellular models to study fibrogenesis of diverse tissues. Supported by substantial in vivo data, a large body of evidence indicates that myofibroblast differentiation induced by the profibrotic cytokine transforming growth factor beta is driven by a prooxidant shift in redox homeostasis due to elevated production of NADPH oxidase 4 (NOX4)-derived hydrogen peroxide and supported by concomitant decreases in nitric oxide/cGMP signaling and reactive oxygen species (ROS) scavenging enzymes. Fibroblast-to-myofibroblast differentiation can be inhibited and reversed by restoring redox homeostasis using antioxidants or NOX4 inactivation as well as enhancing nitric oxide/cGMP signaling via activation of soluble guanylyl cyclases or inhibition of phosphodiesterases. Current evidence indicates the therapeutic potential of targeting the prooxidant shift in redox homeostasis for the treatment of age-related diseases associated with myofibroblast dysregulation.

Postoperative phosphodiesterase type 5 inhibitor administration increases the rate of urinary continence recovery after bilateral nerve-sparing radical prostatectomy

OBJECTIVES

To investigate the effect of phosphodiesterase type 5 inhibitor on urinary continence recovery after bilateral nerve-sparing radical prostatectomy.

METHODS

We analyzed data of 393 open bilateral nerve-sparing radical prostatectomies carried out between 2005 and 2010. Patients who recovered urinary continence within the first month after catheter removal (n = 52) were excluded. This resulted in 341 evaluable patients. Urinary continence recovery was defined as being completely pad free over a period of 24 h. Patients were stratified according to postoperative daily (n = 58; 17%), on-demand (n = 112; 32.8%) and no (n = 171; 50.1%) phosphodiesterase type 5 inhibitor use. The effect of phosphodiesterase type 5 inhibitor use on urinary continence was assessed using the Kaplan-Meier method. Uni- and multivariable Cox regression analyses were used to test the association between phosphodiesterase type 5 inhibitor and urinary continence recovery after adjusting for cofounders.

RESULTS

At a mean follow up of 36.4 months after surgery (median: 33), 288 patients (84.5%) recovered urinary continence after bilateral nerve-sparing radical prostatectomy. Patients who did not use phosphodiesterase type 5 inhibitor after surgery had lower rates of urinary continence recovery at 1- and 2-year follow up as compared with patients taking phosphodiesterase type 5 inhibitor (67.1 vs 86.7% and 76 vs 94.4%, respectively; P < 0.001). After adjusting for all confounders, multivariable analysis showed that phosphodiesterase type 5 inhibitor use, either on demand or daily, had a positive impact on urinary continence recovery (P = 0.03).

CONCLUSIONS

Patients taking phosphodiesterase type 5 inhibitor have higher urinary continence recovery rates as compared with patients left untreated after bilateral nerve-sparing radical prostatectomy. An improvement in sphincteric and pelvic floor blood supply might be responsible for this beneficial effect associated with the use of phosphodiesterase type 5 inhibitor.

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.

A systematic review and meta-analysis on the use of phosphodiesterase 5 inhibitors alone or in combination with α-blockers for lower urinary tract symptoms due to benign prostatic hyperplasia

CONTEXT

Several randomized controlled trials (RCTs) on phosphodiesterase type 5 inhibitors (PDE5-Is) have showed significant improvements in both lower urinary tract symptoms (LUTS) and erectile dysfunction (ED) in men affected by one or both conditions, without a significant increase in adverse events. However, the results are inconsistent.

OBJECTIVE

Perform a systematic review and meta-analysis of available prospective and cross-sectional studies on the use of PDE5-Is alone or in combination with α1-adrenergic blockers in patients with LUTS/benign prostatic hyperplasia (BPH).

EVIDENCE ACQUISITION

A systematic search was performed using the Medline, Embase, and Cochrane Library databases through September 2011 including the combination of the following terms: LUTS, BPH, PDE5-Is, sildenafil, tadalafil, vardenafil, udenafil, α-blockers, and α1-adrenergic blocker. The meta-analysis was conducted according to the guidelines for observational studies in epidemiology.

EVIDENCE SYNTHESIS

Of 107 retrieved articles, 12 were included in the present meta-analysis: 7 on PDE5-Is versus placebo, with 3214 men, and 5 on the combination of PDE5-Is with α1-adrenergic blockers versus α1-adrenergic blockers alone, with 216 men. Median follow-up of all RCTs was 12 wk. Combining the results of those trials, the use of PDE5-Is alone was associated with a significant improvement of the International Index of Erectile Function (IIEF) score (+5.5; p<0.0001) and International Prostate Symptom Score (IPSS) (-2.8; p<0.0001) but not the maximum flow rate (Q(max)) (-0.00; p=not significant) at the end of the study as compared with placebo. The association of PDE5-Is and α1-adrenergic blockers improved the IIEF score (+3.6; p<0.0001), IPSS score (-1.8; p = 0.05), and Q(max) (+1.5; p<0.0001) at the end of the study as compared with α-blockers alone.

CONCLUSIONS

The meta-analysis of the available cross-sectional data suggests that PDE5-Is can significantly improve LUTS and erectile function in men with BPH. PDE5-Is seem to be a promising treatment option for patients with LUTS secondary to BPH with or without ED.

Testosterone regulates smooth muscle contractile pathways in the rat prostate: emphasis on PDE5 signaling

Testosterone (T) plays a permissive role in the development of benign prostatic hyperplasia (BPH), and phosphodiesterase 5 inhibitors (PDE5is) have been found to be effective for BPH and lower urinary tract symptoms (LUTS) in clinical trials. This study investigated the effect of T on smooth muscle (SM) contractile and regulatory signaling pathways, including PDE5 expression and functional activity in prostate in male rats (sham-operated, surgically castrated, and castrated with T supplementation). In vitro organ bath studies, real-time RT-PCR, Western blot analysis, and immunohistochemistry were performed. Castration heavily attenuated contractility, including sensitivity to phenylephrine with SM myosin immunostaining revealing a disrupted SM cell arrangement in the stroma. PDE5 was immunolocalized exclusively in the prostate stroma, and orchiectomy signficantly reduced PDE5 immunopositivity, mRNA, and protein expression, along with nNOS and ROKβ mRNA, whereas it increased eNOS plus α(1a) and α(1b) adrenoreceptor expression in castrated animals. The PDE5i zaprinast significantly increased prostate strip relaxation to the nitric oxide donor sodium nitroprusside (SNP) in control but not castrated rats. But SNP alone was more effective on castrated rats, comparable with sham treated with SNP plus zaprinast. T supplementation prevented or restored all above changes, including SNP and zaprinast in vitro responsiveness. In conclusion, our data show that T positively regulates PDE5 expression and functional activities in prostate, and T ablation not only suppresses prostate size but also reduces prostatic SM contractility, with several potential SM contraction/relaxation pathways implicated. Zaprinast findings strongly suggest a major role for PDE5/cGMP in this signaling cascade. PDE5 inhibition may represent a novel mechanism for treatment of BPH.